1. science
2. physics

Generation of Cold Argon Plasma Jet at the End of Flexible
Plastic Tube
Konstantin G. Kostov1*, Munemasa Machida2 and Vadym Prysiazhnyi1
1
Universidade Estadual Paulista – UNESP, Campus in Guaratinguetá – FEG
Guaratinguetá, SP 12516-410, Brazil
2
Universidade Estadual de Campinas – UNICAMP, Instituto de Física – IFGW
Campinas, SP 13083-859, Brazil
*Corresponding author: [email protected]
Abstract This brief communication reports a new method for generation of cold
atmospheric pressure plasma jet at the downstream end of a flexible plastic tube. The
device consists of a small chamber where dielectric barrier discharge (DBD) is ignited in
Argon. The discharge is driven by a conventional low frequency AC power supply. The
exit of DBD reactor is connected to a commercial flexible plastic tube (up to 4 meters
long) with a thin floating Cu wire inside. Under certain conditions an Ar plasma jet can
be extracted from the downstream tube end and there is no discharge inside the plastic
tube. The jet obtained by this method is cold enough to be put in direct contact with
human skin without electric shock and can be used for medical treatment and
decontamination.
Index Terms: Atmospheric pressure plasma jet, Nonthermal plasma, Plasma propagation in plastic tube
In the last decades, cold atmospheric pressure plasma jets (APPJs) have attracted much
attention due to their versatility, low-cost operation and also ability to produce reactive chemistry at
room temperature [1]. These facts make the plasma jets very attractive for applications in the
biomedical field. An interesting feature of APPJs is their ability to penetrate and propagate inside
small holes and flexible dielectric tubes [2]. Delivery of cold plasma through flexible tube in a
specific location can be very useful for endoscopic applications in medicine, such as treatment of
colorectal and pancreas cancers [3-5]. Therefore, the development of appropriate plasma sources for
in vivo treatments has been subject of intense research. So-called plasma needle reported in [3]
produced cold He plasma on the tip of a thin electrode inserted into a 10-cm-long flexible catheter.
The electrode was connected directly to a RF power supply and the catheter could be bent up to 30°.
This device had only limited length and since the electrode was directly connected to the power
arXiv:1411.3853v1 [physics.optics] 14 Nov 2014
New Design of Electrostatic Mirror Actuators for
Application in High-Precision Interferometry
H Wittel1 , S Hild2 G Bergmann1 , K Danzmann1 and
K A Strain2
E-mail: [email protected]
1
Max–Planck–Institute for Gravitational Physics and Leibniz University of
Hannover, D-30167 Hannover, Germany
2 SUPA, School of Physics and Astronomy, The University of Glasgow, Glasgow,
G12 8QQ, UK
Abstract. We describe a new geometry for electrostatic actuators to be used
in sensitive laser interferometers. The arrangement consists of two plates at the
sides of the mirror (test mass), and therefore does not reduce its clear aperture
as a conventional electrostatic drive (ESD) would do. Using the sample case of
the AEI-10m prototype interferometer, we investigate the actuation range and
influences of relative misalignment of the ESD plates in respect to the test mass.
We find that in the case of the AEI-10 m prototype interferometer, this new kind
of ESD could provide a range of 0.28 µm when operated at a voltage of 1 kV. In
addition, the geometry presented is shown to provide a reduction factor of about
100 in the magnitude of actuator motion coupling to test mass displacement.
We show that therefore in the specific case of the AEI-10m interferometer it is
possible to mount the ESD actuators directly on the optical table, without spoiling
the seismic isolation performance of the triple stage suspension of the main test
masses.
PACS numbers: 04.80.Nn, 95.75.Kk
1. Motivation
Interferometric gravitational wave detectors, such as GEO 600 [1], Advanced LIGO
(aLIGO) [2], Advanced Virgo [3] and KAGRA [4] are large laser interferometers with
the mirrors/test masses hung at the bottom of multi-stage pendulum chains. For the
operation of these detectors, it is necessary to have low-noise, contact-free actuators
for controlling the longitudinal and angular degrees of freedom of the mirrors. This
is traditionally done with either magnet-coil actuators or electrostatic drives (ESDs).
GEO 600 has operated since 2001 with ESDs as the main longitudinal actuators for
controlling the differential arm length. Based on this experience, ESDs are now
employed in aLIGO, using a very similar configuration to the original GEO 600 design.
The GEO/aLIGO ESDs are designed in the form of a metallic comb structure that has
been coated onto a reaction mass and is located a few millimeters behind the mirror.
Schematic drawings and a photograph of this conventional ESD setup are shown in
Figure 1. The ESD on the reaction mass needs its own seismic isolation, to avoid
the coupling of ground motion to the seismically isolated test mass. Therefore, it is
also hung as the lowest stage of a multi stage pendulum, which again requires its own
Two-neutrino double-beta decay of
150
Nd to excited final states in
150
Sm
M.F. Kidd,∗ J.H. Esterline, S. W. Finch, and W. Tornow
Department of Physics, Duke University, Durham, North Carolina 27708, USA and
Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA
(Dated: November 17, 2014)
Background: Double-beta decay is a rare nuclear process in which two neutrons in the nucleus are converted to
two protons with the emission of two electrons and two electron anti-neutrinos.
Purpose: We measured the half life of the two-neutrino double-beta decay of
150
Sm by detecting the de-excitation gamma rays of the daughter nucleus.
150
Nd to excited final states of
arXiv:1411.3755v1 [nucl-ex] 13 Nov 2014
Method: This study yields the first detection of the coincidence gamma rays from the 0+
1 excited state of
150
Sm. These gamma rays have energies of 333.97 keV and 406.52 keV, and are emitted in coincidence through
+
+
a 0+
1 →21 →0gs transition.
Results: The enriched Nd2 O3 sample consisted of 40.13 g 150 Nd and was observed for 642.8 days at the Kimballton Underground Research Facility, producing 21.6 net events in the region of interest. This count rate gives
20
a half life of T1/2 = (1.07+0.45
years. The effective nuclear matrix element was found
−0.25 (stat) ± 0.07(syst.)) × 10
+0.0098
to be 0.0465−0.0054 . Finally, lower limits were obtained for decays to higher excited final states.
Conclusions: Our half-life measurement agrees within uncertainties with another recent measurement in which
no coincidence was employed. Our nuclear matrix element calculation may have an impact on a recent neutrinoless
double-beta decay nuclear matrix element calculation which implies the decay to the first excited state in 150 Sm
is favored over that to the ground state.
I.
INTRODUCTION
The main motivation for studying double-beta decay
is clear: to shed light upon the nature of the neutrino.
Though much has been discovered in the field of the neutrino since its conception and later discovery, some very
basic traits remain unknown. Two of these are the Majorana or Dirac nature of the neutrino, and the particle’s
mass. Observation of neutrinoless double-beta (0νββ)
decay would answer the question of the nature of the
neutrino while simultaneously determining the mass, assuming the nuclear matrix elements (NMEs) for that particular nuclear transition are known. Here, the study of
two-neutrino double-beta (2νββ) decay can prove useful by providing experimental data which can be used
to test and calibrate theoretical models needed to calculate 0νββ NMEs [1]. A study of the rate of the 2νββ
decay of 150 Nd to excited final states of 150 Sm will be
described. This work took place both at Triangle Universities Nuclear Laboratory (TUNL) and at Kimballton
Underground Research Facility (KURF).
The 2νββ decay rate, λ, can be described by the following equation,
2ν 2
λ = G2ν |MF2ν − MGT
| ,
(1)
where G2ν contains phase space integrals and relevant
constants and is dependent on the Q-value of the decay,
2ν
and MF2ν − MGT
represents the Fermi (F) and GamowTeller (GT) components of the 2νββ decay NMEs. Ideal
nuclei for 2νββ decay studies have a high Q-value and
large NMEs. There are 35 nuclei that undergo 2νββ,
∗
Now at Tennessee Technological University, PO Box 5051,
Cookeville, TN 38505; [email protected]
but only 11 (48 Ca, 76 Ge, 82 Se, 96 Zr, 100 Mo, 110 Pd, 116 Cd,
124
Sn, 130 Te, 136 Xe, and 150 Nd) have a Q-value which is
practical for experimental use. This Q-value restriction
is about 2 MeV; below that, such a rare decay could
get overwhelmed by natural radiation. Of the 11 aforementioned nuclei, the double-beta decay to the ground
state of ten has been measured: 48 Ca, 76 Ge, 82 Se, 96 Zr,
100
Mo, 116 Cd, 128 Te, 130 Te, 150 Nd, 136 Xe and (not previously listed) 238 U (see [2] for an excellent compilation of
these results). However, the neutrinoless mode has not
yet been observed.
Besides the Q-value, other quantities which can be considered in order to maximize the experiment’s success in
detecting double-beta decay include natural abundance,
availability of the isotope, possibility of enrichment, and
source cost. To optimize the source efficiency, the number of isotope nuclei must be maximized, which is heavily
dependent on the abundance, enrichment possibility, and
availability of the isotope. One of the best candidates for
0νββ searches is 150 Nd. It has the second highest Q-value
(Qββ =3.37 MeV) and the largest phase-space factor of
all 0νββ candidates [3], and has a natural abundance of
5.64%. Although 150 Nd is strongly deformed, calculations by Fang et al. [3] show that the deformation suppresses the 0νββ NME by only about 40%.
Very recently, a novel decay channel of the scissors
+
154
mode 1+
state (0+
Gd
sc to the first excited 0
1 ) of
was reported by Beller et al. [4], implying a much
larger matrix element than previously thought for the
0νββ decay to the 0+
1 state in the shape transitional
regions of the N=90 isotones. In fact, it was argued in [4] that the 0νββ decay of 150 Nd to the 0+
1
state in 150 Sm may be slightly favored over the transition to the 0+ ground state due to the calculated
0ν +
nuclear matrix element ratio M0ν (0+
1 )/M (0gs )=1.6.
+
If the reduced phase space for the 01 transition is
arXiv:1411.3968v1 [physics.ins-det] 14 Nov 2014
Parallel Neutrino Triggers using GPUs for an underwater telescope
Bachir Bouhadef 1 , Mauro Morganti1,2 , Giuseppe Terreni1
for the KM3Net-It Collaboration
1
2
INFN, Sezione di Pisa, Polo Fibonacci, Largo B. Pontecorvo 3, 56127 Pisa,Italy
Accademia Navale di Livorno, viale Italia 72, 57100 Livorno, Italy
DOI: will be assigned
Graphics Processing Units are high performance co-processors originally intended to improve the use and the acceleration of computer graphics applications. Because of their
performance, researchers have extended their use beyond the computer graphics scope.
We have investigate the possibility of implementing and speeding up online neutrino trigger algorithms in the KM3Net-It experiment using a CPU-GPU system. The results of a
neutrino trigger simulation on NEMO Phase II tower and a KM3-It 14 floors Tower are
reported.
1
Introduction
A neutrino telescope is a tool used to increase our knowledge and to answer fundamental
questions about the Universe. Following the success of the IceCube experiment [1], which is a
km3 size telescope in the ice at south pole, and of the ANTARES experiment [2], an underwater
telescope with a volume of 0.4km3 , the European scientific community is going to construct a
neutrino telescope similar to but larger than IceCube called Km3Net in the Mediterranean Sea.
The NEMO [3] and NESTOR [4] are R&D experiments for the same purpose. All these optical
telescopes use a Photomultiplier Tube (PMT) or a group of it as a Detection Unit (DU). The
NEMO collaboration have already deployed a tower of 32 single PMT DUs. For the much larger
Km3Net Telescope, thousands of DUs will be used to detect the muons passage produced by
undersea neutrino interactions. This large number of sensors will lead to a huge amount of data
to be filtered by any trigger algorithm. In the case of the ANTARES telescope the amount
of data acquired in a second is 0.3-0.5 GB, and many CPUs are used for such a task. The
general strategy of data analysis for an online trigger is that each CPU works on a Time Slice
of the data coming from the underwater telescope [3], and this is a kind of parallel work. In the
present work, we describe the study of using a Graphical Processor Unit (GPU) to implement a
trigger algorithm and to simplify it. In addition, the use of GPU-CPU leads to power, hardware
and time saving. The parallel version of the trigger algorithm is shown to be suitable for an
online muon track selection, and was tested on simulated data of the NEMO Towers of 32 and
84 (KM3Net-It tower) single PMT DUs.
GPUHEP2014
1
FLAVOUR(267104)-ERC-83
November 17, 2014
arXiv:1411.3980v1 [hep-ph] 14 Nov 2014
Addressing Hadronic Uncertainties in Extractions of φs
Robert Knegjens1
TUM Institute for Advanced Study,
Lichtenbergstraße 2a, 85748 Garching, GERMANY
In light of recent LHC results for the extraction of the Bs mixing phase φs ,
we can already conclude that if New Physics (NP) is present in this observable,
it is hiding pretty well. Thus, as our hunt continues, we must be weary not to
confuse NP for penguin effects, or vice versa. In this talk the progress made
towards addressing hadronic uncertainties in extractions of φs from Bs → J/ψφ
is reviewed, and the nature of the scalar f0 (980) state, which plays a dominant
role in the extraction of φs from the Bs → J/ψπ + π − decay, is discussed.
PRESENTED AT
The 8th International Workshop on
the CKM Unitarity Triangle (CKM 2014),
Vienna, Austria, September 8-12, 2014
1
1
Work supported by ERC Advanced Grant project “FLAVOUR” (267104).
Introduction
The CP-violating mixing phase φs ∗ of the Bs meson system has long been a promising and
popular probe of New Physics (NP). In principle, it can be extracted from its interference
with the phase ∆φf of any chosen decay mode Bs → f that is common to both Bs flavour
states, provided, of course, that the latter phase shift is known. The decay mode of
choice is Bs → J/ψφ, which has the desirable property that its dominant diagram has a
vanishing phase shift relative to φs , as well as a favourable decay rate and experimental
signature. Yet it also has an Achilles heel: the contribution of penguin diagrams to the
phase shift. Although suppressed, these diagrams introduce hadronic uncertainties that
must be controlled to achieve precise measurements.
The vector-vector nature of the J/ψφ final state gives three transversity (or polarization) amplitudes, two of which are CP-even and one CP-odd [1, 2], necessitating an angular
analysis to disentangle them. Because the φ is observed via its decay to K + K − , a small
S-wave component has also been found to contribute, adding a fourth, CP-odd, amplitude
to the mix [3, 4]. The dominant resonance in this S-wave is the scalar f0 (980) state [5].
This led to a proposal to also extract φs from Bs → J/ψπ + π − [6], which has a dominant
f0 (980) resonance, too [7]. If the f0 (980) can be shown to have a ss composition similar to
the φ, the phase shift associated with this decay mode could be controlled in an analogous
way to those of Bs → J/ψφ.
There has been great progress recently from the LHC experiments in extracting φs . For
the decay mode Bs → J/ψK + K − the following values have been reported:

−1
 −(3.3 ± 2.8)◦ : LHCb (3fb ) [8]
J/ψKK
(6.9 ± 14.6)◦ : ATLAS (5fb−1 ) [9] .
φs (+ ∆φh
)=
(1)

◦
−(1.7 ± 6.5) : CMS (20fb−1 ) [10]
Likewise, for the extraction from Bs → J/ψπ + π − LHCb has reported [11]
φs (+ ∆φJ/ψππ ) = (4 ± 3.9)◦
(2)
These results clearly lie close to the Standard Model (SM) prediction of φSM
= −(2.1 ±
s
0.1)◦ [12], dispelling the possibility of a large NP signal. Thus if there is NP present in the
Bs mixing phase, it must be small and perhaps even be conspiring with the phase shifts
to stay hidden. Thus the dilemma is that without control over the phase shifts, it will
be impossible to conclude whether a future experimental deviation indicates NP, or if no
deviation means no NP.
J/ψφ
In Section 2 we review the control of penguin contributions to the phase shifts ∆φh .
In Section 3 we discuss whether the dominant resonance in Bs → J/ψπ + π − , the scalar
f0 (980), can be interpreted as an ss state. Finally in Section 4 we give a summary.
0
∗
We define φs as the argument of the dispersive part of hBs0 |H|B s i, with phase conventions fixed so
that φSM
= −2βs .
s
1
Few-Body Systems manuscript No.
(will be inserted by the editor)
Rohini M. Godbole · Abhiram Kaushik · Anuradha
Misra · Vaibhav Rawoot
arXiv:1411.3893v1 [hep-ph] 14 Nov 2014
Single Spin Asymmetry in Charmonium Production
Received: date / Accepted: date
Abstract We present estimates of Single Spin Asymmetry (SSA) in the electroproduction of J/ψ
taking into account the transverse momentum dependent (TMD) evolution of the gluon Sivers function
and using Color Evaporation Model of charmonium production. We estimate SSA for JLab, HERMES,
COMPASS and eRHIC energies using recent parameters for the quark Sivers functions which are fitted
using an evolution kernel in which the perturbative part is resummed up to next-to-leading logarithms
(NLL) accuracy. We find that these SSAs are much smaller as compared to our first estimates obtained
using DGLAP evolution but are comparable to our estimates obtained using TMD evolution where we
had used approximate analytical solution of the TMD evolution equation for the purpose.
Keywords Charmonium, SSA, TMD evolution
1 Introduction
Transverse Single Spin Asymmetries (SSA’s) arise in the scattering of a transversely polarized nucleon
off an unpolarized nucleon (or virtual photon) target when the final observed hadrons have asymmetric
distribution in the transverse plane perpendicular to the beam direction depending on the polarization
vector of the scattering nucleon. One of the two major theoretical approaches to explain these asymmetries is the Transverse Momentum Dependent (TMD) approach[1; 2] which is based on a pQCD
factorization scheme which includes the spin and TMD effects in the collinear factorization scheme.
An important Transverse Momentum Dependent Distribution (TMD) is the Sivers function which is
related to the density of unpolarized partons in a transversely polarized nucleon.
The number density of partons inside proton with transverse polarization S, three momentum
p and intrinsic transverse momentum k⊥ of partons, is expressed in terms of the Sivers function,
∆N fa/p (x, k⊥ ), as
1
ˆ⊥ )
p×k
fˆa/p↑ (x, k⊥ ) = fˆa/p (x, k⊥ ) + ∆N fa/p↑ (x, k⊥ )S · (ˆ
2
Anuradha Misra
Department of Physics, University of Mumbai, SantaCruz(East), Mumbai-400098, India.
E-mail: [email protected]
Rohini Godbole · Abhiram Kaushik
Indian Institute of Science, Bangalore, India-560012
E-mail: [email protected], [email protected]
Vaibhav Rawoot
Institute of Mathematical Sciences, Chennai, India-600113
E-mail: [email protected]
(1)
The effect of uu diquark suppression in proton splitting in
Monte Carlo event generators
V. Uzhinsky1,2 , A. Galoyan3
Monte Carlo event generators assume that protons split into (uu)-diquarks and d-quarks
with a probability of 1/3 in strong interactions. It is shown in this paper that using a
value of 1/6 for the probability allows one to describe at a semi-quantitative level the NA49
Collaboration data for p + p → p + X reactions at 158 GeV/c. The Fritiof (FTF) model
of Geant4 was used to simulate the reactions. The reduced weight of the (uu)-diquarks in
protons is expected in the instanton model.
Most of the Monte Carlo event generators of multi-particle production assume that nucleons split
into diquarks and quarks in strong interactions. In particular, protons split into (ud)-diquarks and uquarks with a probability of 2/3, and into (uu)-diquarks and d-quarks with a probability of 1/3. At the
same time, there are various physical signatures that the probabilities can be different [1]. For example,
it was assumed in the papers [2], as in many other papers, that the (ud)–u configuration completely
dominates in the proton wave function. This was motivated be the instanton model [3] of the QCD
vacuum. According to that model, quark-quark interactions are flavor-dependent: they are non-zero only
if quarks have different flavors. Thus, (uu)-diquarks must be suppressed in protons [4]. The true weight
of the (uu)–d configuration can be estimated using the NA49 Collaboration data [5].
The NA49 Collaboration presented high precision data on particle production in pp interactions at
158 GeV/c including xF , pT and rapidity distributions of various particles (p, n, π ± , K ± , p¯). As shown
in [6, 7], Monte Carlo event generators based on the Fritiof model [8, 9] cannot satisfactorily describe
the data. The most dramatic situation takes place with a description of the proton spectra. A typical
prediction for the xF -spectrum is shown in Figure 1 and is presented by the solid thin line.
1,0
F
0,8
dn/dx
arXiv:1410.6612v1 [hep-ph] 24 Oct 2014
PACS: 24.10.Lx, 13.85.-t,13.85.Ni, 14.20.-c
0,6
0,4
0,2
pp->p+X, 158 GeV/c
0,0
0,0
0,2
0,4
0,6
0,8
1,0
x
F
Figure 1: xF distributions of protons in pp interactions at 158 GeV/c. Closed points are the
NA49 experimental data [5]. Lines are results of FTF model simulations: standard proton
splitting (solid black), optimal diquark fragmentation function (dashed red), string inversion
(dotted blue), diquark suppression (1/6 instead of 1/3) including the optimal fragmentation
function and the string inversion (solid thick).
1 CERN,
Geneva, Switzerland
of Information Technologies, JINR, Dubna, Russia
3 Veksler and Baldin Laboratory of High Energy Physics, JINR, Dubna, Russia
2 Laboratory
1
Search for heavy neutrinos in K + → µ+ νH decays
arXiv:1411.3963v1 [hep-ex] 14 Nov 2014
A.V. Artamonov,1 B. Bassalleck,2 B. Bhuyan,3, a E.W. Blackmore,4 D.A. Bryman,5 S. Chen,6, 4
I-H. Chiang,3 I.-A. Christidi,7, b P.S. Cooper,8 M.V. Diwan,3 J.S. Frank,3, c T. Fujiwara,9 J. Hu,4 J. Ives,5
A.O. Izmaylov,10 D.E. Jaffe,3 S. Kabe,11, d S.H. Kettell,3 M.M. Khabibullin,10 A.N. Khotjantsev,10
P. Kitching,12 M. Kobayashi,11 T.K. Komatsubara,11 A. Konaka,4 Yu.G. Kudenko,10, 13, 14 L.G. Landsberg,1, d
B. Lewis,2 K.K. Li,3 L.S. Littenberg,3 J.A. Macdonald,4, d J. Mildenberger,4 O.V. Mineev,10 M. Miyajima,15
K. Mizouchi,9 N. Muramatsu,16, e T. Nakano,16 M. Nomachi,17 T. Nomura,9, f T. Numao,4 V.F. Obraztsov,1
K. Omata,11 D.I. Patalakha,1 R. Poutissou,4 G. Redlinger,3 T. Sato,11 T. Sekiguchi,11 A.T. Shaikhiev,10
T. Shinkawa,18 R.C. Strand,3 S. Sugimoto,11, d Y. Tamagawa,15 R. Tschirhart,8 T. Tsunemi,11, g
D.V. Vavilov,1, h B. Viren,3 Zhe Wang,6, 3 Hanyu Wei,6 N.V. Yershov,10 Y. Yoshimura,11 and T. Yoshioka11, i
(E949 Collaboration)
1
Institute for High Energy Physics, Protvino, Moscow Region, 142 280, Russia
Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131
3
Brookhaven National Laboratory, Upton, NY 11973
4
TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3
5
Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
6
Department of Engineering Physics, Tsinghua University, Beijing 100084, China
7
Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794
8
Fermi National Accelerator Laboratory, Batavia, IL 60510
9
Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
10
Institute for Nuclear Research RAS, 60 October Revolution Prospect 7a, 117312 Moscow, Russia
11
High Energy Accelerator Research Organization (KEK), Oho, Tsukuba, Ibaraki 305-0801, Japan
12
Centre for Subatomic Research, University of Alberta, Edmonton, Canada T6G 2N5
13
Moscow Institute of Physics and Technology, 141700 Moscow, Russia
14
National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409 Moscow, Russia
15
Department of Applied Physics, Fukui University, 3-9-1 Bunkyo, Fukui, Fukui 910-8507, Japan
16
Research Center for Nuclear Physics, Osaka University,
10-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
17
Laboratory of Nuclear Studies, Osaka University,
1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
18
Department of Applied Physics, National Defense Academy, Yokosuka, Kanagawa 239-8686, Japan
(Dated: November 17, 2014)
2
Evidence of a heavy neutrino, νH , in the K + → µ+ νH decays was sought using the E949 experimental data with an exposure of 1.70 × 1012 stopped kaons. With the major background from the
radiative K + → µ+ νµ γ decay understood and suppressed, upper limits (90% C.L.) on the neutrino
mixing matrix element between muon and heavy neutrino, |UµH |2 , were set at the level of 10−7 to
10−9 for the heavy neutrino mass region 175 to 300 MeV/c2 .
PACS numbers: 14.60.St, 13.20.Eb
I.
a
b
c
d
e
f
g
h
i
Now at Department of Physics, Indian Institute of Technology
Guwahati, Guwahati, Assam, 781 039, India.
Now at Physics Department, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
Now at 1 Nathan Hale Drive, Setauket, New York 11733.
Deceased.
Now at Research Center for Electron Photon Science, Tohoku
University, Taihaku-ku, Sendai, Miyagi 982-0826, Japan.
Now at High Energy Accelerator Research Organization (KEK),
Oho, Tsukuba, Ibaraki 305-0801, Japan.
Now at Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Now at TRIUMF, 4004 Wesbrook Mall, Vancouver, British
Columbia, Canada V6T 2A3.
Now at Department of Physics, Kyushu University, Higashi-ku,
Fukuoka 812-8581, Japan.
INTRODUCTION
With neutrino mass and mixing confirmed (see [1–
16] and references therein), a natural extension of the
Standard Model (SM) involves the inclusion of sterile
neutrinos which mix with ordinary neutrinos to explain
phenomena that may be inconsistent with the Standard
Model. An example of such a theory is the Neutrino Minimal Standard Model (νMSM) [17, 18]. In this model,
the lightest singlet fermion, (νH )1 , with a mass in the
O(10) keV/c2 region has a very weak mixing with the
other leptons, playing no role in active-neutrino mass
generation, and is sufficiently stable to be a viable dark
matter candidate. The second and third fermions, (νH )2
and (νH )3 with masses M2 and M3 , should be nearly
degenerate in mass in the range from ∼ 100 MeV/c2 to
150 GeV/c2 (|M2 − M3 | ≪ M2,3 ) to generate the baryon
arXiv:1411.3898v1 [hep-ex] 14 Nov 2014
Multiplicity, Jet, and Transverse Mass dependence
of Bose-Einstein Correlations in e+e−- Annihilation∗
Wesley J. Metzger1 ,
1
IMAPP, Radboud University, 6525 AJ Nijmegen, The Netherlands
November 17, 2014
Abstract
Bose-Einstein correlations of pairs of identical charged pions produced
in hadronic Z decays are analyzed for both two- and three-jet events. A
parametrization suggested by the τ -model is used to investigate the dependence of the Bose-Einstein correlation function on track multiplicity, number
of jets, and transverse momentum.
1
Introduction
After a brief review of relevant previous results, new preliminary results are presented on the dependence of the Bose-Einstein correlation function on track and
jet multiplicity and transverse momentum, using a parametrization which has been
found [1] to describe well Bose-Einstein correlations (BEC) in hadronic Z decay,
namely that of the τ -model [2, 3],
∗ This talk was also given at XLIV International Symposium on Multiparticle Dynamics,
Bologna, 8–12 September 2014.
1
arXiv:1411.3879v1 [hep-ex] 14 Nov 2014
Measurement of the top quark mass in topologies
enhanced with single top quarks produced in the
√
t-channel at s = 8 TeV using the ATLAS
experiment
Hendrik Esch1 On behalf of the ATLAS Collaboration.
1
TU Dortmund, Exp. Physik IV, Otto-Hahn-Str. 4, 44227 Dortmund, Germany
E-mail: [email protected]
Abstract. This article presents a measurement of the top quark mass in topologies enhanced
with single top quarks produced in the t-channel produced via weak interactions. The
√
dataset was collected at a centre-of-mass energy of s = 8 TeV with the ATLAS detector
at the LHC and corresponds to an integrated luminosity of 20.3 fb−1 . To determine the
top quark mass a template method is used based on the distribution of the invariant mass
of the lepton and the b-tagged jet as estimator. The result of the measurement is mtop =
172.2 ± 0.7(stat.) ± 2.0(syst.) GeV.
1. Introduction
In addition to the tt¯ pair production via the strong interaction, in proton-proton (pp) collisions
at the LHC, top quarks can also be produced singly via the weak charged-current interactions,
giving another possibility for measuring the top quark mass. The dominant process for single
top quark production is the t-channel exchange of a virtual W -boson. Important differences
from the production mode compared to tt¯, resulting in different sizes of certain systematic
uncertainties, and the fact that the measurement of the top quark mass is obtained from a
statistically independent sample, provide an excellent motivation for such a measurement and
for including it in future combinations with other measurements.
In this article, the first measurement of mtop in topologies enhanced with t-channel single
top quark production with the ATLAS experiment [1] is presented. Production of top quark
pairs also give a significant contribution to the sample, while W t production and s-channel
production only give minor contributions. Events are characterised by an isolated high-pT
charged lepton (electron or muon), missing transverse momentum from the neutrino and exactly
two jets produced by the hadronisation of the b-quark and the light quark in the t-channel.
The main backgrounds are W/Z+jets production, especially in association with heavy quarks,
diboson production, and multijet production via QCD processes. Events from all single top
production processes and tt¯ production are treated as signal in the analysis.
arXiv:1411.3868v1 [hep-ex] 14 Nov 2014
November 17, 2014
+
Recent Experimental Results on Leptonic D(s)
Decays, Semileptonic
D Decays and Extraction of |Vcd(s) |
Gang Rong1
Institute of High Energy Physics, CAS, Beijing, China
+
The recent experimental results on leptonic D(s)
decays, semileptonic D
decays, determinations of decay constants and form factors, as well as extractions of |Vcd | and |Vcs | are briefly reviewed. Global analysis of all exist+
ing measurements of leptonic D(s)
decays and semileptonic D decays yields
|Vcd | = 0.2157 ± 0.0045 and |Vcs | = 0.983 ± 0.011, which are the most precision determinations of these two CKM matrix elements up to date.
PRESENTED AT
The 8th International Workshop on the CKM Unitarity Triangle (CKM
2014),
Vienna, Austria, September 8-12, 2014
1
Work supported in part by the National Natural Science Foundation of China (NSFC) under Contract
No.10935007. I would like to thank Yi Fang and Hailong Ma for many helpful discussions about this
experimental review.
1
Introduction
+
In the Standard Model (SM) of particle physics, the decay rate of D(s)
→ ℓ+ νℓ (where
ℓ = e, µ, or τ ) relates to a product of the decay constant fD+ and the Cabibbo-Kobayashi(s)
Maskawa (CKM) matrix element Vcd(s) by
+
Γ(D(s)
→ ℓ+ νℓ ) =
2

G2F 2
m2  2

2
m m + 1 − 2 ℓ  fD
+ | Vcd(s) | ,
8π ℓ D(s)
mD +
(s)
(1)
(s)
where GF is the Fermi coupling constant, mℓ is the mass of the lepton, and mD+ is the
(s)
+
mass of the D(s)
meson. The differential rate of D → π(K)e+ νe decay relates to a product
of decay form factor
π(K)
f+ (q 2 )
and Vcd(s) by
dΓ
G2
π(K)
= X F3 |~
p
|3 |f+ (q 2 )|2 |Vcd(s) |2 ,
dq 2
24π π(K)
(2)
q2
where is square of the four-momenta transfer, p~π(K) is the three-momentum of the π (K)
meson in the rest frame of the D meson, and X is a factor due to isospin, which equals to 1
0
for D 0 → π − e+ νe , D 0 → K − e+ νe and D + → K e+ νe , and equals to 1/2 for D + → π 0 e+ νe .
With precision measurements of these decay rates one can more precisely determine the
π(K)
decay constants fD+ and form factors f+ (0) as well as these CKM matrix elements. The
(s)
π(K)
precisely measured values of fD+ and f+
(s)
(0) can be used to validate LQCD calculations
for these quantities, which can improve determinations of the CKM matrix elements |Vub |,
|Vtd |, and |Vts |. As a consequence, the uncertainty in the overall constraint on the unitarity
triangle of the CKM matrix can be reduced. These can be used for more stringent test of
the SM and search for New Physics beyond the SM.
2
2.1
+
+
→ ℓ+ νℓ decays and decay constants fD(s)
Results on D(s)
+
New results on D(s)
→ ℓ+ νℓ decays
In 2014, the BESIII Collaboration made a measurement of D + → µ+ νµ decays by analyzing
2.92 fb−1 data taken at 3.773 GeV. From 9 hadronic decay modes of D − meson, the BESIII
Collaboration accumulated 1703054 ± 3405 D − tags. In this D − tag sample they observed
409.0 ± 21.2 signal events for D + → µ+ νµ decays and measured the branching fraction
B(D + → µ+ νµ ) = (3.71 ± 0.19 ± 0.06) × 10−4 [1]. They also measured fD+ |Vcd | = 45.75 ±
1.20 ± 0.39 MeV and determined fD+ = 203.2 ± 5.3 ± 1.8. In addition, they extracted
|Vcd | = 0.2210 ± 0.0058 ± 0.0047 [1, 2] from the leptonic D + decays for the first time.
In 2013, the Belle Collaboration made new measurements of Ds+ → µ+ νµ and Ds+ →
τ + ντ decays. By analyzing 913 fb−1 data collected near 10.6 GeV, they measured B(Ds+ →
+
µ νµ ) = (0.531 ± 0.028 ± 0.020)%, B(Ds+ → τ + ντ ) = (5.70 ± 0.21+0.31
−0.30 )% and determined
fDs+ = 255.5 ± 4.2 ± 4.8 ± 1.8 MeV [3].
1
CKM2014
November 17, 2014
arXiv:1411.3866v1 [hep-ex] 14 Nov 2014
D-mixing and indirect CP violation measurements at LHCb
Silvia Borghi1
School of Physics and Astronomy,
The University of Manchester, Manchester, UK
The LHCb experiment collected during run I the world’s largest sample
of charmed hadrons. This sample is used to search for CP violation in charm
and for the measurements of D0 mixing parameters. The measurement of
the D0 −D0 mixing parameters and the search for indirect CP -violation
in two-body charm decays at LHCb experiment are presented.
PRESENTED AT
Presented at the 8th International Workshop on the CKM
Unitarity Triangle (CKM 2014)
Vienna, Austria, September 8-12, 2014
1
1
On Behalf of the LHCb Collaboration
Introduction
The charm sector is a promising field to probe for the effects of physics beyond the
Standard Model (SM). Flavour mixing in the charm sector is now well established [1].
In the SM [2], the CP violation in charm transitions is expected to be small, with
asymmetries up to few O(10−3 ), while it can be enhanced by contribution from New
Physics [3].
The LHCb experiment is dedicated to the study of b and c flavour physics. The
abundance of charm particles produced in LHC offers an unprecedented opportunity
for high precision measurements in the charm sector, including measurements of CP
violation and D0 −D0 mixing.
The results of search for indirect CP violation and the measurements of the mixing
parameters in two body hadronic D0 charm decays are presented here.
2
Mixing and CP violation with D0 → K +π − decays
The flavour mixing occurs because the mass eigenstates (|D1,2 i) are linear combinations
of the flavour eigenstates and they can be written as linear combinations of the
flavour eigenstates |D1,2 i = p|D0 i ± q|D0 i, with complex coefficients p and q which
satisfy |p|2 + |q|2 = 1. The mixing parameters are defined as x ≡ (m1 − m2 )/Γ and
y ≡ (Γ1 − Γ2 )/(2Γ), where m1 , m2 , Γ1 and Γ2 are the masses and the decay widths for
D1 and D2 , respectively, and Γ = (Γ1 + Γ2 )/2. The phase convention is chosen such
that CP |D0 i = −|D0 i.
The first evidence of D0 −D0 oscillation was reported in 2007 by BaBar [4] and Belle
[5]. Now, the mixing in the charm sector is well established with the first observation
by a single measurement with greater than 5 standard deviation significance at the
LHCb experiment [6], confirmed by CDF [7] and Belle [8].
At the LHCb experiment, the charm mixing parameters are determined by the
decay-time-dependent ratio of D0 → K + π − (called wrong sign, WS) to D0 → K − π +
(called right sign, RS) decay rates. The RS decay rate is dominated by Cabibbo
favoured (CF) amplitude. The WS rate arises from the interfering amplitudes of
the doubly Cabibbo-suppressed decay (DCS) and the CF decay following D0 −D0
oscillation. Assuming no CP violation and small mixing parameters (|x| and |y| 1),
this ratio is:
2
p
t x02 + y 2 t
R(t) ≈ RD + RD y 0 +
τ
4
τ
where x0 = x cos δ + y sin δ, y 0 = y cos δ − x sin δ, RD is the ratio of suppressed-tofavoured decay rates, δ is the strong phase difference between
the
DCS decays and
√
the CF decays A (D0 → K + π − ) /A (D0 → K − π + ) = − RD e−iδ .
1
November 17, 2014
arXiv:1411.3773v1 [hep-ex] 14 Nov 2014
Inclusive B decays and exclusive radiative decays by Belle
Yutaro Sato
Kobayashi-Maskawa Institute,
Nagoya University, Nagoya, JAPAN
The b → sγ, b → dγ and b → sℓ+ ℓ− processes are allowed at higher
order via the electroweak loop or box diagrams in the Standard model. It
is sensitive probe to search for new physics beyond the Standard model
because new particles might enter in the loop.
We present preliminary results of branching fraction of the B → Xs γ,
CP asymmetry in the B → Xs+d γ, and the forward-backward asymmetry
in the B → Xs ℓ+ ℓ− . The results are based on a data sample containing
772×106 BB pairs recorded at the Υ(4S) resonance with the Belle detector
at the KEKB e+ e− collider.
PRESENTED AT
The 8th International Workshop
on the CKM Unitarity Triangle (CKM 2014)
Vienna, Austria, September 8–12, 2014
1
Introduction
The b → sγ, b → dγ and b → sℓ+ ℓ− processes are allowed at higher order via the
electroweak loop or box diagrams in the Standard model (SM). It is sensitive probe
to search for new physics beyond the SM because new particles might enter in the
loop. In this report, we present results of inclusive or semi-inclusive measurements
about electroweak penguin processes. Inclusive measurement are preferable to exclusive measurements because of lower theoretical uncertainties, although they are
experimentally more challenging.
2
Branching Fraction of the B → Xsγ
For this analysis a “sum of exclusive” approach is chosen, i.e. we measure as many
exclusive Xs modes as possible and then sum them up to extrapolate inclusive branching fraction. We reconstruct the B meson from a high energy photon and one of the
38 Xs final states. We require the photon candidate with energy 1.8 GeV < Eγ∗ < 3.4
GeV in the center-of-mass (CM) frame.
The dominant background comes from e+ e− → qq(u, d, s, c) continuum events,
which is suppressed using mainly event shape information. For an effective background rejection, we employ a neural network based on the software package “NeroBayes” package [1]. When π 0 from the ρ emits a high energy photon in the B →
D (∗) ρ+ decay, it looks like the signal. To veto such backgrounds, we reconstruct D
candidates of the major decay modes with combinations of particles used in the Xs
reconstruction, and veto events with reconstructed D mass close to the nominal D
mass.
The signal yields are extracted by an maximum likelihood fit to the beam-constrained
mass, Mbc . To minimize the systematic uncertainty from modeling of the Xs mass
distribution, we divide the data into 19 bins of Xs mass in the region 0.6 GeV/c2 <
MXs < 2.8 GeV/c2 . Maximum Xs mass corresponds to a minimum photon energy of
1.9 GeV. Figure 1 shows the partial branching fraction as a function of MXs . Total
branching fraction in MXs < 2.8 GeV/c2 is obtained from the sum of 19 MXs bins:
B(B → Xs γ) = (3.51 ± 0.17 ± 0.33) × 10−4 ,
(1)
where the first uncertainty is statistical and the second is systematic. To compare
theoretical prediction, the experimental result is extrapolated to photon energy in
the B rest frame above 1.6 GeV with extrapolation factor [2]:
B(B → Xs γ) = (3.74 ± 0.18 ± 0.35) × 10−4 ,
(2)
which is consistent with SM prediction [3] within 1.3σ and the most precise result of
any sum-of-exclusives approach.
1
Mon. Not. R. Astron. Soc. 000, 000–000 (0000)
Printed 17 November 2014
(MN LATEX style file v2.2)
Angular Power Spectra with Finite Counts
Sheldon S. Campbell
Center for Cosmology and AstroParticle Physics (CCAPP) and Department of Physics, The Ohio State University
191 W. Woodruff Ave., Columbus, OH 43210
In original form 2014 October 23
arXiv:1411.4031v1 [astro-ph.CO] 24 Oct 2014
ABSTRACT
Angular anisotropy techniques for cosmic diffuse radiation maps are powerful
probes, even for quite small data sets. A popular observable is the angular power
spectrum; we present a detailed study applicable to any unbinned source skymap
S(n) from which N random, independent events are observed. Its exact variance,
which is due to the finite statistics, depends only on S(n) and N ; we also derive
an unbiased estimator of the variance from the data. First-order effects agree with
previous analytic estimates. Importantly, heretofore unidentified higher-order effects are found to contribute to the variance and may cause the uncertainty to
be significantly larger than previous analytic estimates—potentially orders of
magnitude larger. Neglect of these higher-order terms, when significant, may
result in a spurious detection of the power spectrum. On the other hand, this
would indicate the presence of higher-order spatial correlations, such as a large
bispectrum, providing new clues about the sources. Numerical simulations are
shown to support these conclusions. Applying the formalism to an ensemble of
Gaussian-distributed skymaps, the noise-dominated part of the power spectrum
uncertainty is significantly increased at high multipoles by the new, higher-order
effects. This work is important for harmonic analyses of the distributions of
diffuse high-energy γ-rays, neutrinos, and charged cosmic rays, as well as for
populations of sparse point sources such as active galactic nuclei.
Key words: methods: data analysis – methods: statistical – methods: analytical
– cosmology: diffuse radiation – gamma-rays: diffuse background – neutrinos.
1
INTRODUCTION
An important experiment in astronomy is measuring the
angular distribution of points on the sky from the arrival
directions of incident radiation. When distance information for sources is unavailable (or too unreliable), then
techniques for quantifying their two-dimensional angular
distribution become essential. These methods are important for analyzing distributions of point sources, as well
as incident radiation from diffuse sources (or those that
appear to be, due to insufficient angular resolution).
The information contained in angular distributions
depends on the application. Temperature anisotropies of
the cosmic microwave background (CMB) contains information about primordial fluctuations at the epoch of lastscattering, as well as the distribution of matter and ionized gas at subsequent epochs that affected the propagation of the microwaves (e.g., WMAP Collaboration 2013;
Planck Collaboration 2014). The distribution of galaxies (e.g., Hayes, Brunner, & Ross 2012; Ho et al. 2012)
or quasars (Leistedt et al. 2013; Ho et al. 2013) probes
the large scale structure of matter. High-energy messenc 0000 RAS
gers, the focus of this article, have special challenges:
charged cosmic rays are deflected, γ-rays can be attenuated, and neutrinos are detected only in small numbers.
Directional detection of these messengers allows inferences about their sources and propagation effects.
One popular measure of the angular distribution is
its power spectrum Cℓ , the mean-square-amplitudes of
fluctuations with wavelength π/ℓ radians, specified with
a basis of spherical harmonics Yℓm . These are particularly convenient observables because they characterize
the angular scales of anisotropy and they are statistically orthogonal, hCℓ Cℓ′ i − hCℓ i hCℓ′ i ∝ δℓℓ′ , for full-sky
Gaussian-distributed skymaps. Since the Cℓ are 2-point
functions, they represent the lowest order deviations from
isotropy. Such harmonic analyses are also applied to the
clustering of three-dimensional cosmological data in thin
spherical shells to simplify redshift distortion effects (e.g.,
Fisher, Schar, & Lahav 1994; Percival et al. 2004).
One intent for analyses of galaxy surveys is to determine the statistical properties of the large scale structure
in terms of their typical spatial correlations. These correlations contain information about the physics of the early
arXiv:1411.4030v1 [astro-ph.CO] 14 Nov 2014
Prepared for submission to JCAP
Calculation of primordial
abundances of light nuclei including
a heavy sterile neutrino
M. E. Mosquera,a,b O. Civitareseb,1
a Facultad
de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata,
Paseo del Bosque, (1900) La Plata, Argentina
b Department of Physics, University of La Plata,
c.c. 67 (1900), La Plata, Argentina
E-mail: [email protected], [email protected]
Abstract. We include the coupling of a heavy sterile neutrino with active neutrinos in the
calculation of primordial abundances of light-nuclei. We calculate neutrino distribution functions and primordial abundances, as functions depending on a renormalization of the sterile
neutrino distribution function (a), the sterile neutrino mass (ms ) and the mixing angle (φ).
Using the observable data, we set constrains on these parameters, which have the values
a < 0.60, sin2 φ = 0.15 and ms ≈ 4 keV, for a fixed value of the baryon to photon ratio.
When the baryon to photon ratio is allowed to vary, its extracted value is in agreement with
the values constrained by Planck observations and by the Wilkinson Microwave Anisotropy
Probe (WMAP). It is found that the anomaly in the abundance of 7 Li persists, in spite of
the inclusion of a heavy sterile neutrino.
1
Corresponding author.
APCTP-Pre2014-015
arXiv:1411.3974v1 [astro-ph.CO] 14 Nov 2014
CMB probes on the correlated axion
isocurvature perturbation
Kenji Kadotaa, Jinn-Ouk Gongb,c,
Kiyomoto Ichikid,e and Takahiko Matsubarad,e
a Center
for Theoretical Physics of the Universe, Institute for Basic Science, Daejeon 305-811, Korea
b Asia Pacific Center for Theoretical Physics, Pohang 790-784, Korea
c Department of Physics, Postech, Pohang 790-784, Korea
d Department of Physics, Nagoya University, Nagoya 464-8602, Japan
e Kobayashi-Maskawa Institute for the Origin of Particles and the Universe
Nagoya University, Nagoya 464-8602, Japan
Abstract
We explore the possible cosmological consequence of the gravitational coupling between
the inflaton and axion-like fields. In view of the forthcoming cosmic microwave background
(CMB) polarization and lensing data, we study the sensitivity of the CMB data on the
cross-correlation between the curvature and axion isocurvature perturbations. Through
a concrete example, we illustrate the explicit dependence of the scale dependent crosscorrelation power spectrum on the axion parameters.
DESY 14-217
SFB/CPP-14-90
November 17, 2014
arXiv:1411.3916v1 [hep-lat] 14 Nov 2014
Form factors for Bs → K`ν decays in Lattice QCD
Felix Bahr1 , Fabio Bernardoni, John Bulava, Anosh Joseph,
Alberto Ramos, Hubert Simma, Rainer Sommer
John von Neumann Institute for Computing (NIC), DESY, Platanenallee 6,
D-15738 Zeuthen, Germany
We present the current status of the computation of the form factor
f+ (q 2 ) for the semi-leptonic decay Bs → K`ν by the ALPHA collaboration. We use gauge configurations which were generated as part of the
Coordinated Lattice Simulations (CLS) effort. They have Nf = 2 nonperturbatively O(a) improved Wilson fermions, and pion masses down
to ≈ 250 MeV with mπ L ≥ 4. The heavy quark is treated in nonperturbative Heavy Quark Effective Theory (HQET).
We discuss how to extract the form factors from the correlation functions and present first results for the form factor at q 2 = 21.23 GeV2
extrapolated to the continuum. Next-to-leading order terms in HQET
and the chiral extrapolation still need to be included in the analysis.
PRESENTED AT
8th International Workshop on the CKM Unitarity Triangle
(CKM 2014), Vienna, Austria, September 8-12, 2014
1
1
Speaker
Introduction
Determinations of the CKM matrix element |Vub | from different exclusive (and inclusive) decays tend to disagree at the ∼ 2 − 3σ level [1]. Both theoretical and
experimental improvements are needed to clarify the situation.
In this work, we report on our ongoing effort to non-perturbatively determine the
form factors for Bs → K`ν decays from Lattice Quantum Chromodynamics (LQCD)
with Nf = 2 sea quarks. Although no experimental data is available yet for this
decay, the heavier spectator s-quark renders the LQCD computations technically
simpler than for B → π`ν, and thus provides a good starting point to gain solid
control on all systematic errors (and to make an LQCD prediction).
The decay amplitude
for
Bs → K`ν is proportional to |Vub | times the hadronic
matrix element K(pK )Vµ Bs (pBs ) of the vector current Vµ (x) = ψ u (x)γµ ψb (x). The
matrix element is parametrised by two form factors, f0 (q 2 ) and f+ (q 2 ), which depend
on q 2 = (pBs − pK )2 , the invariant mass of the lepton pair. In the limit of vanishing
lepton masses only f+ (q 2 ) contributes to the decay rate.
|Vub | can then be determined by combining the differential decay rate from experiment with f+ (q 2 ) from theory. In principle, it is sufficient to do this at a single
value of q 2 . In practice, experimental data is provided over a range (of bins) of q 2 ,
and one can use the BCL paramterisation [2] to express the form factor f+ (q 2 ) as a
continuous function of q 2 . Then, a theoretical prediction of f+ (q 2 ), e.g. from LQCD,
for at least a single q 2 allows to extract |Vub |.
Here we report on preliminary work to study the feasibility of a precise determination of the form factor in the continuum limit and at a fixed q 2 .
2
HQET on the lattice
On the lattice (with spatial extent L and lattice spacing a) the large mass of the b
quark gives rise to a hierarchy of scales
L−1 mπ ≈ 140 MeV mB ≈ 5 GeV a−1 ,
(1)
which cannot be directly simulated with present computing resources. Instead, we
follow the strategy devised by the ALPHA collaboration [3] to treat the heavy quark
within the framework of non-perturbative Lattice HQET. It is an expansion in inverse
powers of the heavy quark mass mh and valid for kaon momenta pK mh . In practice,
we require pK . 1 GeV. A key feature of Lattice HQET is that it is (believed to be)
non-perturbatively renormalisable order by order in 1/mh , and thus the computations
have a well-defined continuum limit. The expectation value of a product of local fields,
O, up to and including O(1/mh ) in HQET on the lattice is
X
X
hOi = hOistat + ωkin a4
hOOkin (x)istat + ωspin a4
hOOspin (x)istat ,
(2)
x
x
1
Systematic Investigation of Negative Cooper-Frye Contributions in Heavy Ion
Collisions Using Coarse-grained Molecular Dynamics
D. Oliinychenko,1, 2, ∗ P. Huovinen,1, 3, † and H. Petersen1, 3, ‡
1
arXiv:1411.3912v1 [nucl-th] 14 Nov 2014
Frankfurt Institute for Advanced Studies, D-60438 Frankfurt am Main, Germany
2
Bogolyubov Institute for Theoretical Physics, Kiev 03680, Ukraine
3
Institut f¨
ur Theoretische Physik, Goethe-Universit¨
at, D-60438 Frankfurt am Main, Germany
In most heavy ion collision simulations involving relativistic hydrodynamics, the Cooper-Frye
formula is applied to transform the hydrodynamical fields to particles. In this article the so-called
negative contributions in the Cooper-Frye formula are studied using a coarse-grained transport
approach. The magnitude of negative contributions is investigated as a function of hadron mass,
collision energy in the range of Elab = 5–160A GeV, collision centrality and the energy density
transition criterion defining the hypersurface. The microscopic results are compared to negative
contributions expected from hydrodynamical treatment assuming local thermal equilibrium.
The main conclusion is that the number of actual microscopic particles flying inward is smaller
than the negative contribution one would expect in an equilibrated scenario. The largest impact
of negative contributions is found to be on the pion rapidity distribution at midrapidity in central
collisions. For this case negative contributions in equilibrium constitute 8–13% of positive contributions depending on collision energy, but only 0.5–4% in cascade calculation. The dependence on
the collision energy itself is found to be non-monotonous with a maximum at 10-20A GeV.
I.
INTRODUCTION
Relativistic hydrodynamics is nowadays the standard
approach for modeling ultrarelativistic heavy-ion collisions at highest RHIC (Relativistic Heavy Ion Collider)
and LHC (Large Hadron Collider) energies. These dynamical descriptions are either based on ideal [1, 2] or
dissipative hydrodynamics [3, 4] and describe the entire expansion fluid dynamically. In so called hybrid approaches [5, 6] only the early hot and dense stage of the
expansion is described using hydrodynamics and the later
dilute stage by hadron transport.
Most of these models use a conceptually similar procedure: Given an initial condition, the hydrodynamic equations are solved in the whole forward light cone. Near
the boundary of vacuum and at the late times of evolution hydrodynamics is not applicable any more, when
the density is small and the mean free path is larger
than the system size. Therefore, models switch to an
off-equilibrium microscopic description in terms of particles in this region. In hybrid approaches particles can
scatter, while other models allow only free-streaming and
resonance decays. In any case, the most commonly used
way to convert the fluid-dynamical fields to particles, a
process that we call here ’particlization’, is by using the
Cooper-Frye formula.
The Cooper-Frye formula assumes particlization to
take place on infinitesimally thin three-dimensional hypersurface in four-dimensional space-time. This hypersurface Σ is usually determined a posteriori from hydrodynamical solution in the whole forward light cone, usually as a hypersurface of constant time, energy density,
∗
†
‡
[email protected]
[email protected]
[email protected]
temperature, or Knudsen number. Particle distributions
on an infinitesimal element of hypersurface, dΣ, are calculated using the following formula:
p0
d3 N
= pµ dσµ f (p) ,
d3 p
(1)
h
µ
i−1
p uµ −µ
where f (p) = exp
±
1
, dσµ is a normal
T
four-vector of hypersurface with length equal to the area
of the infinitesimal surface element, uµ = γ(1, v) is the
flow velocity of the fluid, and T and µ are temperature
and chemical potential of the fluid, respectively. This formula was obtained by Cooper and Frye [7] with the main
feature that it respects four-momentum conservation.
There is, however, a conceptual problem with this formula. Where the surface is space-like, i.e., its normal
3
vector dσµ is space-like, dd3Np < 0 for some p. This can
be easily seen in the local rest frame of a space-like surface (which always exists since vsurf < c for space-like
3
surfaces), where pµ dσµ = p · n and thus dd3Np < 0 for momenta directed inward the surface. On the other hand,
for those time-like surfaces which normal vector points
3
toward the future (i.e., dσ0 > 0), dd3Np > 0 for any p.
This can be also understood as follows: surface is ”escaping” faster than the speed of light, so no particle can
cross it inward. (For a summary of the properties of
time-like and space-like surfaces, see Table I).
3
If dd3Np is interpreted as a phase-space density, negative
values of it are clearly unphysical, but instead of giving
a literal phase-space density, Cooper-Frye formula rather
counts the world lines of particles crossing the surface
element dΣ, and gives positive weight to particles moving “outward” and negative weight to particles moving
3
“inward”. Thus the negative values of dd3Np , the so-called
negative Cooper-Frye contributions, refer to particles fly-
DESY 14–206
arXiv:1411.3834v1 [physics.comp-ph] 14 Nov 2014
Simple, Parallel, High-Performance Virtual Machines for Extreme
Computations
Bijan Chokoufe Nejada,b , Thorsten Ohlb , J¨urgen Reutera
a DESY
b University
Theory Group, Notkestr. 85, D-22607 Hamburg
of W¨urzburg, Emil-Hilb-Weg 22, 97074 W¨urzburg, Germany
Abstract
We introduce a high-performance virtual machine (VM) written in a numerically fast language
like Fortran or C to evaluate very large expressions. We discuss the general concept of how to
perform computations in terms of a VM and present specifically a VM that is able to compute
tree-level cross sections for any number of external legs, given the corresponding byte code from
the optimal matrix element generator, O’Mega. Furthermore, this approach allows to formulate
the parallel computation of a single phase space point in a simple and obvious way. We analyze
hereby the scaling behaviour with multiple threads as well as the benefits and drawbacks that are
introduced with this method. Our implementation of a VM can run faster than the corresponding
native, compiled code for certain processes and compilers, especially for very high multiplicities,
and has in general runtimes in the same order of magnitude. By avoiding the tedious compile
and link steps, which may fail for source code files of gigabyte sizes, new processes or complex
higher order corrections that are currently out of reach could be evaluated with a VM given
enough computing power.
Keywords: Virtual Machine, High-Performance Computing, Automation of perturbative
calculations, Higher Orders, Parallel Computation
1. Introduction
Computations in high energy physics tend to hit the limits of what is computationally feasible. Setting demanding grid computations aside, one encounters even in perturbative calculations expressions of cross sections of enormous size. Such computations for the Large Hadron
Collider (LHC), its upgrade the High Luminosity LHC (HL-LHC) or the planned International
Linear Collider (ILC) are and keep getting more challenging as cross sections are needed for a
high number of external particles and to increasing precision to match the experimental efforts.
When facing such problems, a compromise has to be made, in order to have a maintainable and
extendible solution for the developer and at the same time fast execution of the code. The latter
Email addresses: [email protected] (Bijan Chokoufe Nejad), [email protected]
(Thorsten Ohl), [email protected] (J¨urgen Reuter)
Preprint submitted to Computer Physics Communications
November 17, 2014
SNSN-XXX-YY
November 17, 2014
arXiv:1411.3743v1 [nucl-ex] 13 Nov 2014
Proton Charge Radius and Precision Tests of QED
Jan C. Bernauer
Laboratory for Nuclear Science
Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA
02139
The “proton radius puzzle” remains unsolved since it was established
in 2010. This paper summarizes the current state and gives an overview
over upcoming experiments.
PRESENTED AT
XXXIV Physics in Collision Symposium
Bloomington, Indiana, September 16–20, 2014
transition from 2S to a higher state like 8S or 8D are measured. The proton radius
is then extracted using simultaneous fit of the radius and the Rydberg constant.
Currently published measurements are typically less precise than the results from
scattering experiments. Combining the available data, however, leads to an extraction
with similar uncertainties.
1.3
Muonic Hydrogen spectroscopy
In recent years, it became possible to study muonic hydrogen, the bound state of a
proton and a muon, with spectroscopy. The muon, because of its larger mass, has
a 200 times smaller orbit and with that an about 2003 higher probability of being
inside the proton. Consequently, the finite size effect is substantially larger, making
a more precise extraction of the radius possible. The published results quote more
than ten times smaller uncertainties.
1.4
The puzzle
Figure 1 shows the result of recent determinations. For scattering, the results from
[1, 2] and [3] are presented. The former is the result of a measurement of more than
1400 cross sections, about twice of all other existing proton form factor data. The
latter is an extraction using almost all available data except the Mainz data set. It
is therefore independent. The H-spectroscopy result is taken from the global fit of
CODATA 2010 [4]. These measurements are all in agreement with each other; a
combined result of the electron measurements is shown as “electron avg”. In contrast
to this, the two published results from muon spectroscopy [5, 6], are consistent with
each other, but more than 7 standard deviations away from the electron result.
The discrepancy, dubbed the “proton radius puzzle”, has driven a wide range of
theoretical and experimental efforts, and has even found its way into popular science
literature [7]. Since the publication of [1] and [6] in 2010, it has withstood all attempts
at a solution.
2
Possible solutions
The puzzle has prompted a lot of research, leading to a large number of papers trying
to solve the discrepancy. However, many have been ruled out by further studies.
None has seen widespread acceptance by the community so far. In this section, some
of the proposed solutions will be discussed. Due to the sheer number, this paper can
only highlight some of the ideas. Instead, I will try to give a categorization and a
personal perspective.
2
November 17, 2014
arXiv:1411.4026v1 [hep-ph] 14 Nov 2014
The like-sign dimuon asymmetry and New Physics
Miguel Nebot1
Centro de F´ısica Te´orica de Part´ıculas,
Instituto Superior T´ecnico, Universidade de Lisboa,
Av. Rovisco Pais 1, 1049-001 Lisbon, PORTUGAL
The measurement by the D0 collaboration of a large like-sign dimuon
asymmetry deviates significantly from Standard Model expectations. New
Physics may be invoked to account for such a deviation. We analyse how
generic extensions of the Standard Model where the Cabibbo-KobayashiMaskawa 3 × 3 mixing matrix is enlarged can accommodate a significant
enhancement of AbSL with respect to standard expectations through enhancements of the individual semileptonic asymmetries AdSL and AsSL in
0
0
the Bd0 –B d and Bs0 –B s systems. The potential enhancement reachable
in this class of scenario is, nevertheless, insufficient to reproduce the D0
measurement.
PRESENTED AT
8th International Workshop on the CKM Unitarity Triangle
(CKM 2014),
Vienna, Austria, September 8-12, 2014
1
Work supported by Funda¸c˜
ao para a Ciˆencia e a Tecnologia (FCT, Portugal) through the
projects CERN/FP/123580/2011 and CFTP-FCT Unit 777.
1
Introduction
Phenomena related to Flavour Physics and CP violation constitute a fundamental
window to probe the Standard Model (SM) and its extensions. In this context, one
results from the D0 collaboration has received much attention: the measurement of
the like-sign dimuon asymmetry AbSL [1]. The value reported by the D0 collaboration
[1] is approximately “3σ” away from SM expectations, and a large number of works
have explored the potential of models beyond the SM to reproduce it [2]. In the
following, we first review the SM predictions and then address NP analyses, focusing
on scenarios where the mixing matrix is enlarged with respect to the usual 3 × 3
unitary Cabibbo-Kobayashi-Maskawa.
2
Mixing and asymmetries in Bq meson systems
(q)
In the SM, the dispersive Bq → B q transition amplitude, M12 , is dominated by one
loop box diagrams with virtual t quarks:
h
i
G2 M 2
(q)
M12
= F 2W MBq fB2 q BBq ηB (Vtb Vtq∗ )2 S0 (xt ) .
(1)
12π
SM
(q)
The absorptive part, Γ12 , is on the contrary dominated by intermediate real (onshell) u and c quarks. The SM short-distance prediction [3] requires a Heavy Quark
(q)
Expansion giving Γ12 as an expansion in αs (mb ) and Λ/mb . Our interest lies on the
flavour structure, which has, in general, the following form
"
#
(q)
Γcc
Γuc
Γuu
Γ12
12
∗
∗ 2
=−
(Vcb Vcq∗ )2 + 2 12
(Vub Vuq
Vcb Vcq∗ ) + 12
(Vub Vuq
) ,
(2)
(q)
(q)
(q)
(q)
M12
M12
M12
M12
and in particular in the SM the flavour structure is
"
#
(q)
∗
∗ 2
(Vcb Vcq∗ )2
Vub Vuq
Vcb Vcq∗
(Vub Vuq
)
Γ12
∝ Γcc
+ 2Γuc
+ Γuu
.
12
12
12
(q)
(Vtb Vtq∗ )2
(Vtb Vtq∗ )2
(Vtb Vtq∗ )2
M12 SM
(3)
cc
uc
uu
Γab
12 are −Γ12 = c, −2Γ12 = 2c − a, −Γ12 = b + c − a, where
a = (10.5 ± 1.8) · 10−4 , b = (0.2 ± 0.1) · 10−4 , c = (−53.3 ± 12.0) · 10−4 .
(4)
In an expansion in powers of (mc /mb )2 , it is important to stress that at zero-th order
only c is present. Unitarity of the CKM mixing matrix, through the orthogonality
∗
condition Vub Vuq
+ Vcb Vcq∗ + Vtb Vtq∗ = 0, implies
"
#
"
#
(q)
∗
∗ 2
Vub Vuq
Vub Vuq
Γ12
= K(q) c + a
+b
,
(5)
∗
∗
(q)
V
V
V
V
M12
tb tq
tb tq
SM
1
IPMU14-0341
Does asymmetric dark matter always lead to an anti-neutrino signal?
Hajime Fukuda, Shigeki Matsumoto and Satyanarayan Mukhopadhyay1
1
Kavli IPMU (WPI), The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
Under rather generic assumptions, we show that in the asymmetric dark matter (ADM) scenario,
the sign of the B − L asymmetry stored in the dark matter sector and the standard model sector
are always the same. One particularly striking consequence of this result is that, when the dark
matter decays or annihilates in the present universe, the resulting final state always involves an
anti-neutrino. As a concrete example of this, we construct a composite ADM model and explore
the feasibility of detecting such an anti-neutrino signal in atmospheric neutrino detectors.
arXiv:1411.4014v1 [hep-ph] 14 Nov 2014
INTRODUCTION
The experimental probes of particle dark matter at
present are primarily motivated by the most widely studied paradigm of weakly interacting massive particles
(WIMP). The appeal of the WIMP hypothesis lies in
the fact that a particle with mass typically in the range
of 100 to 1000 GeV correctly leads to the observed dark
matter (DM) density − a fact that is largely independent
of the details of the model under consideration, assuming
a standard thermal history of the universe [1]. Intriguing
alternatives, however, do exist in the DM model space,
which lead to equally generic predictions as in the WIMP
scenarios. Asymmetric dark matter (ADM) is one such
model which has been widely studied. An ADM with a
mass in the range of 1 to 10 GeV leads to the observed
ratio of baryon to DM densities, which is again largely
independent of the model details in a standard thermal
history of the universe [2].
With the above alternative solution to the DM puzzle
in mind, it is important to look for experimental signatures that can discriminate an ADM from a WIMP. In
order to maintain thermal equilibrium in the early universe, WIMP’s must interact with the standard model
(SM) particles. In most cases, this leads to unsuppressed
WIMP annihilations to SM final states in the present
universe as well, which are being looked for in various
indirect detection experiments [3]. Usually, for a WIMP
particle which is identical to its anti-particle, the annihilation final states include equal number of SM particles
and anti-particles of a given variety. Although ADM’s
must also interact with the SM sector to be in chemical
equilibrium in the early universe, there is a crucial difference in the expected decay or annihilation products at
present universe. The ADM particles are charged under
the U (1)B−L symmetry, which is conserved in all interactions. This leads to a final state with a non-zero B − L
charge, with different numbers of SM particles and antiparticles of a given species − a fact that can be utilized
to distinguish an ADM from a WIMP [4].
This has interesting consequences in the signatures of
the ADM particle. For example, the same interaction
leading to the chemical equilibrium can cause decay or
annihilation of the ADM particles at present universe.
In such a case, we find that it would always produce
final states with a positive B − L charge.1 This fact implies that the resulting final states always involve an antineutrino. This is because, in the SM, neutrinos are the
only stable particles carrying a non-zero B − L charge
and are electrically neutral. On the other hand, other
stable particles carrying a B − L charge, namely the electron and the proton, are electrically charged and must
be produced in pairs to make the final state electrically
neutral. Such pairs, however, do not carry a net B − L
charge. This fact leads to a rather striking signal in large
volume atmospheric neutrino detectors which can separate neutrinos from anti-neutrinos to a good accuracy: an
anti-neutrino signal with an energy of 1 to 10 GeV. We
emphasize here that although the prediction for either
only a neutrino or only an anti-neutrino signal depending
upon the B − L charge of the surviving ADM particle was
made in past studies, our results show that chemical equilibrium determines the surviving ADM (anti-)particle to
always have a positive B − L charge, independent of the
interaction term involved.
In what follows, we first prove that the sign of the
B − L asymmetry stored in the dark matter sector and
the SM sector are always the same under rather generic
assumptions on the ADM scenario. Thereafter, as a concrete example, we construct an explicit model of composite ADM, which is a hidden baryon of a confining SU (3)D
gauge symmetry. Finally, we discuss its decay signatures
in the form of anti-neutrinos and their detectability in
ongoing and near future experiments.
B − L ASYMMETRY STORED IN DM SECTOR
In the ADM scenario, the B − L asymmetry is postulated
to be generated by a baryogenesis mechanism in the early
universe. Leptogenesis [5] is one promising way to generate the baryon asymmetry, which at the same time enables us to explain tiny neutrino masses via the see-saw
mechanism [6]. Since the ADM particle is charged under
1
The convention followed by us fixes the baryon number of the
universe observed today (in visible matter) to be positive.
INR-TH/2014-026
Decaying light particles on board the SHiP (I):
Signal rate estimates for hidden photons
D. Gorbunov,1, 2, ∗ A. Makarov,1, † and I. Timiryasov1, 3, ‡
1
Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 117312, Russia
2
Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia
3
Physics Department, Moscow State University, Vorobievy Gory, Moscow 119991, Russia
For the extension of the Standard model with light hidden photons we present preliminary estimates of the signal rate expected at the recently proposed fixed target SHiP experiment exploiting
CERN SPS beam of 400 GeV protons.
arXiv:1411.4007v1 [hep-ph] 14 Nov 2014
I.
INTRODUCTION: THE EXPERIMENT AND
THE MODEL TO BE TESTED
Unsolved phenomenological problems — neutrino oscillations, dark matter phenomena, baryon asymmetry
of the Universe — definitely ask for an extension of the
Standard model of particle physics (SM). It is natural to
find the corresponding new particles at a mass scale not
much higher than the electroweak scale. Otherwise the
hierarchy problem arises in the scalar sector: quantum
corrections of heavy particles push the SM Higgs boson
mass up to their mass scale. While LHC scrutinizes thoroughly the (sub)TeV scale, there is a logical possibility to
have so far elusive new physics at (much) lower scale. The
absence of any direct evidence of the new physics may be
attributed to the weakness of interaction between known
and new particles. In search for such new physics the
superior are experiments operating on the high intensity
frontier.
An example of this type of experiments is SHiP (Search
for Hidden Particles [1]), the recently proposed [2] new
fixed target experiment at CERN SPS 400 GeV proton beam. The original motivation [3] was to search for
O(1) GeV sterile neutrinos of νMSM: one of the most economic extensions of the SM capable of explaining all the
three aforementioned phenomenological problems with
only three new fields (singlet with respect to SM gauge
groups fermions) added to the SM, see [4] for review.
Mixing between singlet fermions and active neutrinos is
responsible for both the singlet production in decays of
heavy mesons (generated by protons on target) and subsequent singlet decays into SM particles (the main signature for the SHiP detector), see [5] for details. The flux of
secondary particles from proton scatterings is suppressed
by the very dense (tungsten) dump placed downstream.
The main idea is to have detector large (5×5 m2 ×50 m
[2]) and place it as close to the target as possible (at
a distance of about 60 m [2]) in order to maximize the
number of potential singlet decays within the detector
fiducial volume and still have the background under control. This makes SHiP a universal tool to probe any new
∗
†
‡
[email protected]
[email protected]
[email protected]
physics which introduces sufficiently light and long-lived
particles produced by protons on target and then decaying
into the SM particles.
In this paper we consider one of the examples of such
new physics providing with long-lived light particles to
be searched for at SHiP: models with massive hidden
photons. The SM Lagrangian LSM is extended in the
following way:
1 0 0µν 0 µν m2A0 0 0µ
F
+ Fµν F +
Aµ A , (1)
L = LSM − Fµν
4
2
2
where A0µ is a massive gauge field of a new (dubbed dark)
0
≡ ∂µ A0µ − ∂ν A0µ , and is the parameter
U 0 (1) group, Fµν
of kinetic mixing. This mixing provides effective coupling
between massive photon A0 and pairs of the SM charged
particles, which determines the model phenomenology.
Hidden photon may be a messenger of the hidden sector,
that is responsible for (some of) the unsolved problems
we started with (see e.g. [6] for dark matter). Present
phenomenological limits on and mA0 are shown in Fig. 1.
The purpose of this work is to estimate the number of
FIG. 1. Present limits on the hidden photon model parameter
space, see [7], [8], [9] for details. Red shaded region shows the
expected limits from SHiP, see Sec. IV.
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–6
Signatures of anomalous Higgs couplings in angular asymmetries
of H → Z`+ `− and e+ e− → HZ
M. Benekea , D. Boitoa,b,∗, Y.-M. Wanga,c
arXiv:1411.3942v1 [hep-ph] 14 Nov 2014
a Physik
Department T31, Technische Universit¨at M¨unchen
James-Frack-Straße 1, D-85748 Garching, Germany
b Instituto de F´ısica, Universidade de S˜
ao Paulo,
Rua do Mat˜ao Travessa R, 187, 05508-090, S˜ao Paulo, SP, Brazil
c Institut f¨
ur Theoretische Teilchenphysik und Kosmologie, RWTH Aachen University,
D-52056 Aachen, Germany
Abstract
Parametrizing beyond Standard Model physics by the S U(3) × S U(2)L × U(1)Y dimension-six effective lagrangian,
we study the impact of anomalous Higgs couplings in angular asymmetries of the crossing symmetric processes
H → Z`+ `− and e+ e− → HZ. In the light of present bounds on d = 6 couplings, we show that some asymmetries
can reveal BSM effects that would otherwise be hidden in other observables. The d = 6 HZγ couplings as well as
(to a lesser extent) HZ`` contact interactions can generate asymmetries at the several percent level, albeit having less
significant effects on the di-lepton invariant mass spectrum of the decay H → Z`+ `− . The higher di-lepton invariant
mass probed in e+ e− → HZ can lead to complementary anomalous coupling searches at e+ e− colliders.
Keywords: Higgs physics, dimension-six effective Lagrangian, Beyond Standard Model physics
1. Introduction, operators and couplings
The discovery of a light boson H with mass around
125 GeV at the LHC [1, 2] has opened a window to a
new sector in the search for physics beyond the Standard Model (BSM). The new state is compatible with a
SM Higgs, with the quantum numbers J P = 0+ being
highly favoured by the data [3, 4]. The study of signal
strengths of the new state has shown that the Higgs couplings are compatible with SM predictions. Evidence
for BSM physics has proven to be more elusive than
previously expected; the SM appears to be a good effective field theory (EFT) at the least up to the energies
probed by the first run of LHC.
In the spirit of an EFT, the SM should be supplemented with all operators with dimension d > 4 constructed from its fields and compatible with its symI TUM
preprint HEP-968/14
∗ Speaker
metry. In this work we adopt the linear realization of
the S U(2)L × U(1)Y symmetry [5, 6]. The leading corrections to Higgs physics within this scheme arise from
the dimension-six operators, that are suppressed by the
large scale Λ characteristic of BSM physics, and generate anomalous Higgs boson couplings.
In the search for BSM physics in the flavour sector of
the standard model, in particular in the case of flavourchanging neutral currents, dedicated observables were
constructed from the angular distribution of the decay
B → K ∗ ``. The angular distribution of the decay H →
Z`+ `− offers similar possibilities that we exploit in this
work.
The study of the decay H → Z`+ `− , with the on-shell
Z also decaying into `+ `− , has a long history. Its angular distributions were instrumental in the determination
of the Higgs quantum numbers [3, 4], as suggested long
ago (see e.g. Refs. [7, 8, 9, 10]). After the Higgs discovery, it has been suggested that the di-lepton mass distri-
The muonic hydrogen Lamb shift and the proton radius
Clara Peset∗
Grup de F´ısica Te`orica and IFAE, Universitat Aut`onoma de Barcelona, 08193 Bellaterra, Barcelona
Abstract
arXiv:1411.3931v1 [hep-ph] 14 Nov 2014
m2
We obtain a model independent expression for the muonic hydrogen Lamb shift up to O(mµ α6 , mµ α5 mµ2 ). The hadronic
ρ
effects are controlled by the chiral theory, which allows for their model independent determination. We give their
complete expression including the pion and Delta particles. Out of this analysis and the experimental measurement of
the muonic hydrogen Lamb shift we determine the electromagnetic proton radius: r p =0.8412(15) fm. This number is
at 6.8σ variance with respect to the CODATA value. The parametric control of the uncertainties allows us to obtain a
model independent determination of the error, which is dominated by hadronic effects.
Keywords: Chiral Lagrangians, Bound states, Heavy quark effective theory, Specific calculations
1. Introduction
The recent measurement of the muonic hydrogen (µp)
Lamb shift, E(2P3/2 ) − E(2S 1/2 ) [1, 2],
exp
∆E L = 202.3706(23) meV
(1)
and the associated determination of the electromagnetic
proton radius: r p = 0.84087(39) fm has led to a lot
of controversy. The reason is that this number is 47σ away from previous determinations of this quantity
coming from hydrogen and electron-proton (ep) scattering [3, 4].
In order to asses the significance of this discrepancy it
is of fundamental importance to perform the computation of this quantity in a model independent way. In
this respect, the use of effective field theories (EFTs)
is specially useful. They help organizing the computation by providing with power counting rules that asses
the importance of the different contributions. This becomes increasingly necessary as higher order effects are
included. Even more important, these power counting rules allow to parametrically control the size of the
higher order non-computed terms and, thus, give an estimate of the error.
The EFT approach is specially convenient in the case
of bound states where there are different, well separated
scales, namely, the hard scale or reduced mass (mr ), the
soft scale or typical momentum (mr v ∼ mr α) and the
ultrasoft scale or typical binding energy (mr v2 ∼ mr α2 ).
In the case of µp we need to deal with several scales:
m p ∼ mρ ,
mµ ∼ mπ ∼ mr ≡
mµ m p
,
m p + mµ
mr α ∼ me .
from which we obtain the main expansion parameters
by considering ratios of them
mµ 1 me mr α mr α 2
mπ
1
∼
≈
∼
∼
∼α≈
. (2)
m p m p 9 mr
mr
mr α
137
These, together with the counting rules given by the
EFT provide the necessary tools to perform the full analysis of the Lamb shift in µp up to leading-log O(mµ α6 )
m2
terms and leading O(mµ α5 mµ2 ) hadronic effects.
ρ
In our approach we combine the use of Heavy Baryon
Effective Theory (HBET) [5, 6], Non-Relativistic QED
(NRQED) [7] and, specially, potential NRQED (pNRQED) [8–10]. Partial results following this approach
can be found in [11–13] (see [14] for a review). In Ref.
[15] we computed the n = 2 Lamb shift with accum2
racy O(mµ α6 , mµ α5 mµ2 ). A more detailed account of the
ρ
hadronic part can be found in [16]. These proceedings
are based on the work carried out in Refs. [15, 16].
2. Lamb shift and extraction of the proton radius
∗ Speaker
Email address: [email protected] (Clara Peset)
Preprint submitted to Nuc. Phys. (Proc. Suppl.)
All contributions to the Lamb shift up to the order of our
interest are summarized in Table 1. Together they sum
November 17, 2014
QCD sum-rule results for heavy-light meson decay constants
and comparison with lattice QCD
arXiv:1411.3890v1 [hep-ph] 14 Nov 2014
Wolfgang Lucha
Institute for High Energy Physics, Austrian Academy of Sciences
Nikolsdorfergasse 18, A-1050 Vienna, Austria
Dmitri Melikhov
Institute for High Energy Physics, Austrian Academy of Sciences
Nikolsdorfergasse 18, A-1050 Vienna, Austria
D.V. Skobeltsyn Institute of Nuclear Physics
M.V. Lomonosov Moscow State University, 119991, Moscow, Russia
Silvano Simula
Istituto Nazionale di Fisica Nucleare, Sezione Roma Tre
Via della Vasca Navale 84, I-00146 Roma, Italy
Updated predictions for the decay constants of the D, Ds , B and Bs
mesons obtained from Borel QCD sum rules for heavy-light currents are
presented and compared with the recent lattice averages performed by the
Flavor Lattice Averaging Group. An excellent agreement is obtained in
the charm sector, while some tension is observed in the bottom sector.
Moreover, available lattice and QCD sum-rule calculations of the decay
constants of the vector D ∗ , Ds∗ , B ∗ and Bs∗ mesons are compared. Again
some tension in the bottom sector is observed.
PRESENTED AT
the 8th International Workshop on
the CKM Unitarity Triangle (CKM 2014)
Vienna, Austria, September 8–12, 2014
1
Leptonic decay constants from QCD sum rules
Leptonic decay constants of pseudoscalar (PS) heavy-light mesons are crucial hadronic
ingredients relevant for the extraction of the Cabibbo-Kobayashi-Maskawa (CKM)
matrix elements from the experimental data on the weak decays of a heavy-light meson
H to a lepton-neutrino pair via flavor-changing transitions [1], H → ℓνℓ , and on the
rare leptonic decays of neutral PS mesons to a charged-lepton pair via flavor-changing
neutral currents [2], H → ℓ+ ℓ− . Moreover, the leptonic decay constants of vector
(V) heavy-light mesons are relevant quantities in the heavy-quark phenomenology,
like, e.g., for describing the contributions of vector poles coupled to weak currents
mediating the semileptonic decays of PS heavy-light mesons.
Within the method of QCD sum rules (QCD-SR) [3, 4] the extraction of the
leptonic decay constants of ground-state PS and V mesons is based on the analysis
of the two-point correlation functions
i
i
Z
Z
i
h
d4 xeip·x h0|T j5 (x)j5† (0) |0i = ΠP S (p2 ) ,
h
i
d4 xeip·x h0|T jν (x)jν†′ (0) |0i =
−gνν ′ +
(1)
pν pν ′
p2
!
ΠV (p2 ) +
pν pν ′ V 2
Π (p ) , (2)
p2 L
where j5 (x) = (mh + mq )q(x)iγ5 h(x) and jν (x) = q(x)γν h(x) are interpolating heavylight quark currents with h = c, b and q = u, d, s.
The correlators ΠP S (p2 ) and ΠV (p2 ) have both a hadronic and a quark-gluon
(OPE) representation. After Borelization one has:
4(2)
−MP2 S(V ) τ
ΠP S(V ) (τ ) = fP2 S(V ) MP S(V ) e
=
Z
∞
(mh +mq )2
+
Z
∞
P S(V )
sphys
P S(V )
P S(V )
ds e−sτ ρhadron (s)
P S(V )
ds e−sτ ρpert (s, µ) + Πpower
(τ, µ) ,
(3)
∗
where fP S(V ) is the leptonic decay constant , MP S(V ) the mass of the ground state,
P S(V )
P S(V )
sphys the threshold for excited states, ρpert the perturbative spectral density,
P S(V )
Πpower
the power corrections containing the contributions of all vacuum condensates
and µ is the subtraction point introduced by the OPE.
P S(V )
The perturbative spectral density ρpert can be expanded as a series of powers
of the strong coupling constant αs (µ) and it has been calculated beyond the leading
order (LO), given by the simple heavy-light loop, by including two- and three-loop
contributions. The NLO corrections, originating from two loops related to gluon
exchanges, are known from Refs. [5, 6] in the case of the PS channel and from Ref. [7]
in the case of the V one. The NNLO contributions for both PS and V correlators
∗
The leptonic decay constants are defined as: fP S MP2 S ≡ h0|j5 (0)|Hi and fV MV εVν ≡
h0|jν (0)|H ∗ i, where εVν is the polarization vector of the H ∗ meson.
1
KUNS-2529, YITP-14-89
Parametric Instability of Classical Yang-Mills Fields under Color Magnetic Background
Shoichiro Tsutsui,1, 2, ∗ Hideaki Iida,1 Teiji Kunihiro,1 and Akira Ohnishi2
arXiv:1411.3809v1 [hep-ph] 14 Nov 2014
1
Department of Physics, Faculty of Science, Kyoto University, Kyoto 606-8502, Japan
2
Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan
(Dated: November 17, 2014)
We investigate instabilities of classical Yang-Mills fields in a time-dependent spatially homogeneous color
magnetic background field in a non-expanding geometry for elucidating the earliest stage dynamics of ultrarelativistic heavy-ion collisions. The background gauge field configuration considered in this article is spatially
homogeneous and temporally periodic, and is alluded by Berges-Scheffler-Schlichting-Sexty (BSSS). We discuss the whole structure of instability bands of fluctuations around the BSSS background gauge field on the
basis of Floquet theory, which enables us to discuss the stability in a systematic way. We find various instability
bands on the (pz , pT )-plane. These instability bands are
√ caused by parametric resonance despite the fact that the
momentum dependence of the growth rate for |p| ≤ B is similar to a Nielsen-Olesen instability. Moreover,
some of instability bands are found to emerge not only in the low momentum
but also in the high momentum
√
region; typically of the order of the saturation momentum as |p| ∼ B ∼ Qs .
PACS numbers: 11.15.Me, 12.38.Gc, 11.10.Wx, 25.75.Nq
I.
INTRODUCTION
Remarkable properties of the quark-gluon plasma (QGP)
have been revealed by the recent ultra-relativistic heavy-ion
experiments at the Relativistic Heavy-Ion Collider (RHIC) at
Brookhaven National Laboratory and the Large Hadron Collider (LHC) at CERN. Hydrodynamic models turned out to
be successful in describing the transverse momentum (pT )spectra and the anisotropic flows (vn ) of hadrons [1–3]. The
observation of large elliptic flow parametrized by v2 suggests
two important features of QGP; nearly perfect fluidity and
early thermalization. The initial spatial eccentricity of the participants seems to be efficiently converted to the final momentum anisotropy. This is only possible when the viscosity is
small enough and the pressure is developed in the early stage.
Hydrodynamic phenomenology suggests that shear viscosity
of QGP is η/s = (1 − 3)/4π. Hydrodynamic analyses also
require a short thermalization time, τth = (0.6 − 1.0)fm/c
which is significantly shorter than that evaluated from transport theories [4, 5]. There are no conclusive scenarios found
yet to explain thermalization in the far-from-equilibrium stage
of heavy-ion collisions.
Some of the promising mechanisms for early thermalization are instabilities which cause rapid growth of a classical
Yang-Mills (CYM) field followed by its decay into particles.
CYM field theory is believed to be a good starting point for
describing the earliest stage of heavy-ion collisions. In the
high energy limit, nuclear wave functions are well expressed
by color glass condensate (CGC) effective field theory [6, 7].
In the framework of CGC, the classical solution gives transversely polarized color electromagnetic fields whose sources
are valence partons in the large x-region. The contact of two
nuclei converts CGC into the state with longitudinally polarized color electromagnetic fields called glasma [8]. Classical
fields in glasma show instabilities, and some of classical gluon
∗ [email protected]
fields grow exponentially, show chaoticity and may decay into
particles via field-particle conversions. Thus instabilities of
classical fields should play important roles in thermalization
in heavy-ion collisions [9–17].
It is known for a long time that an instability occurs in
electromagnetic plasmas when anisotropy is present. When
the particle momentum distribution is anisotropic, the particle
current and the background magnetic field enhance each other.
This is called the Weibel instability [18]. The Weibel instability of the color magnetic field is also expected to emerge in
glasma, and has been discussed as one of the triggers leading
to early thermalization in heavy-ion collisions [10, 11, 19, 20].
The system under a homogeneous and static color magnetic
field shows a different instability. Under a homogeneous color
magnetic field, Landau orbits are formed due to the U(1) component of the color magnetic field and the lowest Landau
modes may become tachyonic. If this is the case, the resultant instability called the Nielsen-Olesen instability [21], is
also expected as a triggering mechanism of the early thermalization in heavy-ion collisions [22–24].
This is not the end of the story. Yet another instability can
occur under a homogeneous but time dependent color magnetic field. This type of instability is alluded by Berges, Scheffler, Schlichting and Sexty (BSSS) [25]. Their analysis based
on the classical statistical simulation suggests that low momentum modes become unstable under the time-dependent
color magnetic field. This instability is seemingly reminiscent
of the Nielsen-Olesen instability, because it is caused by the
homogeneous color magnetic field and the dominant growth
rate has similar longitudinal momentum dependence to that of
the Nielsen-Olesen instability. They also suggest that there
exists a sub-dominant instability band in a high momentum
region. It is caused by the time dependence of the background
field, and thus the underlying nature of the sub-dominant instability is thought to be induced by parametric resonance.
The Nielsen-Olesen instability and the parametric-resonanceinduced instability seem to coexist in their study.
However, the analysis on the nature of the instability has
some ambiguous points to be further elucidated. The Nielsen-
arXiv:1411.3763v1 [hep-ph] 13 Nov 2014
Journal of Physics: Conference Series
The double radiative B¯ → Xsγγ decay
at O(αs) in QCD
Ahmet Kokulu
Department of Mathematical Sciences, University of Liverpool, L69 3BX Liverpool,
United Kingdom
E-mail: [email protected]
Abstract. In these proceedings, we briefly review the individual interference contribution of
the electromagnetic dipole operator O7 to the double differential decay width dΓ77 /(ds1 ds2 )
¯ → Xs γγ at O(αs ) in QCD, which is based on our work in [1]. We define two
for the process B
kinematical variables s1 and s2 as si = (pb − qi )2 /m2b , where pb , q1 , q2 are the momenta of bquark and two photons. While the (renormalized) virtual corrections are worked out exactly for
a certain range of s1 and s2 , we retained in the gluon bremsstrahlung process only the leading
power w.r.t. the (normalized) hadronic mass s3 = (pb − q1 − q2 )2 /m2b in the underlying triple
differential decay width dΓ77 /(ds1 ds2 ds3 ). We found that the double differential decay width,
based on this approximation, is free of infrared- and collinear singularities when summing up
the virtual- and real-radiation corrections, while this was not the case when keeping all powers
in s3 in the gluon bremsstrahlung process due to the configurations allowing collinear photon
emission from the (massless) s-quark. Lastly, we compare our analytical results with those
obtained in a recently extended work [2], where a non-zero strange quark mass was introduced
to regulate the collinear photon configurations.
1. Introduction
Inclusive rare B-meson decays provide a crucial place to probe new physics indirectly. In the
Standard Model (SM) all these processes proceed through loop diagrams (due to GlashowIliopoulos-Maiani mechanism) and thus are relatively suppressed. In the extensions of the SM the
contributions stemming from the diagrams with “new” particles in the loops can be comparable
or even larger than the contribution from the SM. Thus getting experimental information on rare
decays puts stringent constraints on the extensions of the SM or can even lead to a disagreement
with the SM predictions, providing evidence for some “new physics”.
To make a rigorous comparison between experiment and theory, precise SM calculations for
¯ → Xs γ [3] and
the (differential) decay rates are mandatory. While the branching ratios for B
+
−
¯
B → Xs ℓ ℓ are known today even to next-to-next-to-leading logarithmic (NNLL) precision
¯ → Xs γγ discussed in these
(for reviews, see [4, 5]), other branching ratios, like the one for B
proceedings, has been calculated before to leading logarithmic (LL) precision in the SM by
several groups [6, 7, 8, 9] and only recently a first step towards next-to-leading-logarithmic
¯ → Xs γ, the current-current
(NLL) precision was presented by us in [1]. In contrast to B
operator O2 has a non-vanishing matrix element for b → sγγ at order α0s precision, leading to
an interesting interference pattern with the contributions associated with the electromagnetic
Prepared for submission to JHEP
CERN-PH-TH-2014-225
arXiv:1411.3758v1 [hep-ph] 13 Nov 2014
Interactions of a Stabilized Radion and Duality
Zackaria Chacko,a Rashmish K. Mishra,a Daniel Stolarski,b and Christopher B.
Verhaarena
a
Maryland Center for Fundamental Physics, Department of Physics,
University of Maryland, College Park, MD 20742-4111
b
Theory Division, Physics Department, CERN, CH-1211 Geneva 23, Switzerland
Abstract: We determine the couplings of the graviscalar radion in Randall-Sundrum
models to Standard Model fields propagating in the bulk of the space, taking into account
effects arising from the dynamics of the Goldberger-Wise scalar that stabilizes the size of
the extra dimension. The leading corrections to the radion couplings are shown to arise
from direct contact interactions between the Goldberger-Wise scalar and the Standard
Model fields. We obtain a detailed interpretation of the results in terms of the holographic
dual of the radion, the dilaton. In doing so, we determine how the familiar identification
of the parameters on the two sides of the AdS/CFT correspondence is modified in the
presence of couplings of the bulk Standard Model fields to the Goldberger-Wise scalar. We
find that corrections to the form of the dilaton couplings from effects associated with the
stabilization of the extra dimension are suppressed by the square of the ratio of the dilaton
mass to the Kaluza-Klein scale, in good agreement with results from the CFT side of the
correspondence.
Probing GPDs in Ultraperipheral Collisions
D.Yu. Ivanov∗ , B. Pire† , L. Szymanowski∗∗ and J. Wagner∗∗
arXiv:1411.3750v1 [hep-ph] 13 Nov 2014
∗
Sobolev Institute of Mathematics and Novosibirsk State University,630090 Novosibirsk, Russia
†
CPHT, École Polytechnique, CNRS, 91128 Palaiseau, France
∗∗
National Centre for Nuclear Research (NCBJ), Warsaw, Poland
Abstract. Ultraperipheral collisions in hadron colliders give new opportunites to investigate the hadron stucture through
exclusive photoproduction processes. We describe the possibility of measuring the Generalized Parton Distributions in the
Timelike Compton Scattering process and in the production of heavy vector meson.
Keywords: photon: beam , scaling: Bjorken , parton: distribution function , Compton scattering , generalized parton distribution , gluon ,
quark
PACS: 13.60.Fz, 12.38.Bx, 13.88.+e
INTRODUCTION
Besides their primary use for exploring a new energy domain, high energy hadron colliders are powerful sources of
quasi real photons in ultraperipheral collisions [1]. This is usually described through the equivalent photon approximation (EPA) formula that reads
σ AB =
Z
dkA
dnA γB
σ (WA (kA )) +
dkA
Z
dkB
dnB γA
σ (WB (kB ))
dkB
√
where kA,B = 21 xA,B s. and dn
dk is an equivalent photon flux, i.e. the number of photons with energy k.
This opens the possibility for studying many aspects of photon proton, photon nucleus and photon photon collisions
at ultra high energies, particularly at the LHC, many years before the eventual construction of electron-ion colliders
[2]. The high luminosity and energies of these quasi-real photon beams open a new kinematical domain for the study
of exclusive processes which are now understood in the framework of the colinear factorization approach of QCD,
as a powerful tool to our understanding of how quarks and gluons build hadrons. The concept of generalized parton
distributions (GPDs)[3] is central in this respect. In particular the transverse location of quarks and gluons become
experimentally measurable via the transverse momentum dependence of the GPDs [4]. Determining sea-quark and
gluon GPDs in the small skewedness region is an essential program complementary to the determination of the valence
quark GPDs at lower energy electron accelerators.
The golden channel to access GPDs in quasi real photon processes is lepton pair production with a large invariant
mass Q, either in the continuum or near a charmonium resonance such as J/Ψ. In the continuum, the process known
as timelike Compton scattering (TCS) [5] is the timelike analog of the celebrated deeply virtual Compton scattering
(DVCS) which has been and is the subject of intense studies at medium and high energies. J/Ψ production has the
advantage of larger cross sections but may depend on the way the charmonium wave function is described. Both
processes probe the same underlying partonic dynamics.
TIMELIKE COMPTON SCATTERING
The proof of QCD colinear factorization of TCS at leading twist follows the same line as the one for DVCS.
This solidly establishes the validity of the approach. As in the case of DVCS, a purely electromagnetic competing
mechanism, the Bethe-Heitler (BH) mechanism contributes at the amplitude level to the same final state as TCS. This
BH process has a very peculiar angular dependence and overdominates the TCS process if one blindly integrates over
the final phase space. This is the reason why most Monte Carlo programs for ultraperipheral collisions do not consider
the QCD process we are discussing here. A winning strategy consists of choosing kinematics where the amplitudes of
Prepared for submission to JHEP
Big Bang Synthesis of Nuclear Dark Matter
arXiv:1411.3739v1 [hep-ph] 13 Nov 2014
Edward Hardy,a,b Robert Lasenby,a John March-Russell,a,c Stephen M. Westd
a
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road,
Oxford, OX1 3NP, UK
b
Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151, Trieste,
Italy
c
Stanford Institute for Theoretical Physics, Department of Physics, Stanford University,
Stanford, CA 94305, USA
d
Physics Department, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
E-mail: [email protected], [email protected],
[email protected], [email protected]
Abstract: We investigate the physics of dark matter models featuring composite bound
states carrying a large conserved dark “nucleon” number. The properties of sufficiently
large dark nuclei may obey simple scaling laws, and we find that this scaling can determine the number distribution of nuclei resulting from Big Bang Dark Nucleosynthesis. For
plausible models of asymmetric dark matter, dark nuclei of large nucleon number, e.g.
& 108 , may be synthesised, with the number distribution taking one of two characteristic
forms. If small-nucleon-number fusions are sufficiently fast, the distribution of dark nuclei
takes on a logarithmically-peaked, universal form, independent of many details of the initial conditions and small-number interactions. In the case of a substantial bottleneck to
nucleosynthesis for small dark nuclei, we find the surprising result that even larger nuclei,
with size 108 , are often finally synthesised, again with a simple number distribution.
We briefly discuss the constraints arising from the novel dark sector energetics, and the
extended set of (often parametrically light) dark sector states that can occur in complete
models of nuclear dark matter. The physics of the coherent enhancement of direct detection signals, the nature of the accompanying dark-sector form factors, and the possible
modifications to astrophysical processes are discussed in detail in a companion paper.
BONN–TH–2014–15, CERN-PH-TH-2014-226
On the two–loop corrections to the Higgs mass in trilinear R–parity violation
Herbi K. Dreiner,1, ∗ Kilian Nickel,1, † and Florian Staub2, ‡
1
Bethe Center for Theoretical Physics & Physikalisches Institut der Universität Bonn,
53115 Bonn, Germany
2
Theory Division, CERN, 1211 Geneva 23, Switzerland
We study the impact of large trilinear R–parity violating couplings on the lightest CP–even Higgs
boson mass in supersymmetric models. We use the publicly available computer codes SARAH and
SPheno to compute the leading two–loop corrections. We use the effective potential approach. For
<
not too heavy third generation squarks (m
e ∼ 1 TeV) and couplings close to the unitarity bound we
find positive corrections up to a few GeV in the Higgs mass.
arXiv:1411.3731v1 [hep-ph] 13 Nov 2014
I.
INTRODUCTION
On July 4th , 2012 the discovery of the Higgs boson
was announced at CERN [1, 2]. It is not yet established
whether this is the Standard Model (SM) Higgs boson [3–
5]. However, in the SM the Higgs sector suffers from the
hierarchy problem [6], to which supersymmetry (SUSY)
[7, 8] is the most obvious solution. It predicts a wide
range of observables at the Large Hadron Collider (LHC),
for which the first run has finished; Run II is expected to
start in the Spring, 2015.
There is no convincing experimental indication of any
physics beyond the Standard Model (SM) at the LHC1.
This puts pressure on many proposed scenarios for beyond the standard model (BSM) physics, in particular
also SUSY. The simplest SUSY scenario, the constrained
minimal supersymmetric Standard Model (CMSSM) [7],
is now excluded [9], see also [10–13]. However, the MSSM
extended for example by R–parity violation (RpV) operators [14–17] can significantly weaken the collider mass
limits [18–21] and provide an even richer phenomenology
than the MSSM [22–26].
Within SUSY the mass of the Higgs boson is restricted
at tree–level to be less than the mass of the Z 0 –boson.
However realised, the quantum corrections to the mass
can be large [27, 28]. The observed mass of the Higgs
boson, mexp
≈ 125.7 GeV [29–31], is well within the
h
previous predicted allowed range for SUSY models [32].
Such large corrections however typically require very
large mixing in the stop sector and/or a very heavy stop
squark. This in turn is disfavoured by fine–tuning arguments [33, 34].
When extending the MSSM these conclusions can be
modified, e.g. in the NMSSM [35–37]. Here we consider
the Higgs mass in supersymmetric models with RpV. The
∗
†
‡
1
[email protected]–bonn.de
[email protected]–bonn.de
[email protected]
See for example the talk given by O. Buchmüller at the EPS 2013
conference in Stockholm https://indico.cern.ch/event/218030/
session/28/contribution/869/material/slides/.
additional operators contribute to the Higgs mass at the
two–loop level2. This effect is expected to be large especially when involving third generation squarks. We study
¯ and U
¯D
¯D
¯ operators involving
the impact of large LQD
stops and sbottoms on the lightest CP–even Higgs bo¯ are here completely negson mass. (The effects of LLE
ligible.) For this purpose we calculate two–loop Higgs
masses in models beyond the MSSM, but with MSSM
precision, with the public computer tools SARAH [39–43]
and SPheno [44, 45], as recently presented in [46].
This letter is organized as follows: we present in the
next section our conventions for the models we consider,
before we give details about the two–loop calculation in
sec. III. The numerical results are presented in sec. IV,
before we conclude in sec. V.
II.
THE MSSM EXTENDED BY TRILINEAR
R–PARITY VIOLATION
R–parity is a discrete multiplicative Z2 symmetry of
the MSSM, defined as [14–17, 47]
RP = (−1)3(B−L)+2s ,
(1)
where s is the spin of the field and B, L are its baryon
respectively lepton number. We consider the R-parity
conserving superpotential of the MSSM
¯ j Hd + Y ij Qi D
¯ j Hd
WR = Yeij Li E
d
¯ j Hu + µ Hu Hd ,
+Yuij Qi U
(2)
and extend it by trilinear RpV operators [48, 49]
1
¯ k + λ0ijk Li Qj D
¯ k + 1 λ00ijk U
¯ iD
¯ jD
¯k .
λijk Li Lj E
2
2
(3)
We assume the bi–linear term has been rotated away [50].
Here i, j, k = 1, 2, 3 are generation indices, while SU (3)
WR
/ =
2
See also the two–loop RpV renormalization group equations,
which modify the running of the Higgs mass [38].
CP3-Origins-2014-039 DNRF90, DIAS-2014-39, HIP-2014-28/TH.
Self-Interacting Dark Matter through the Higgs Portal
Chris Kouvaris,1, ∗ Ian M. Shoemaker,1, † and Kimmo Tuominen2, ‡
arXiv:1411.3730v1 [hep-ph] 13 Nov 2014
1
CP3 -Origins & Danish Institute for Advanced Study DIAS,
University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
2
Department of Physics and Helsinki Institute of Physics,
P.O.Box 64, FI-00014, University of Helsinki, Finland
We study self-interacting dark matter coupled to the Standard Model via the Higgs portal. We
consider a scenario where dark matter is a thermal relic with strong enough self interactions that
can alleviate the problems of collisionless dark matter. We study constraints from direct detection
searches, the LHC, and Big Bang nucleosynthesis. We show that the tension between these constraints and the need for sufficiently strong self-interactions with light mediators can be alleviated
by coupling the mediator to either active or sterile neutrinos. Future direct detection data offers
great potential and can be used to find evidence of a light mediator and verify that dark matter
scatters via long-range self-interactions.
I.
INTRODUCTION
There appears to be tension between the observations
and simulations of small-scale structure of Collisionless
Cold Dark Matter (CCDM). Observations of dwarf galaxies seem to confirm that the dark matter (DM) density
profile is not cuspy as one gets closer to the center of the
galaxy as is seen in simulations of CCDM [1], but rather
exhibit a flat core [2, 3]. In addition there is the socalled “missing satellite” problem which is the fact that
numerical simulations predict many more dwarf galaxies
than what is currently observed in the Milky Way [4–6].
Furthermore there is the “too big to fail” problem [7]:
it seems that numerical simulations predict dense dwarf
galaxies which cannot host the brightest known dwarf
galaxies. Although one can claim that the the “missing
satellite” problem may be due to the Milky Way being a
statistical fluctuation [8–10], the “too big to fail” problem
due to unobserved dim dwarf galaxies and the cusp/core
problem due to baryonic-DM interactions [11–14], it is
possible that the explanation of all the above problems
is the existence of sizeable DM-DM interactions.
The idea that DM self-interactions may ameliorate
the aforementioned problems has been studied extensively and in various contexts [15–34].
In particular, it was pointed out in [20] that DM interacting with a light force carrier φ that satisfies roughly
2
(mX /10 GeV) (mφ /100 MeV) ∼ 1 (where mφ is the
mass of the particle φ), can facilitate nicely the flat profile at the core of dwarf galaxies for a range of Yukawa
strengths 10−5 < αX < 1, while evading constraints on
self-interactions coming from galactic and cluster scales.
Although such types of DM self-interactions can resolve
some of the problems associated with CCDM, one must
ensure that such self-interactions are not strong enough
to destroy the ellipticity of spiral galaxies or dissociate
∗ Electronic
address: [email protected]
address: [email protected]
‡ Electronic address: [email protected]
† Electronic
the subcluster of the bullet cluster [35]. Depending on
the scenario there can be additional strict constraints.
For example if φ couples to the Standard Model through
a Higgs portal [36–43], one should make sure that φ decays before the start of the Big Bang Nucleosynthesis
(BBN) (∼ 1 sec) so the decay products will not affect
BBN. This constraint sets a minimum interaction coupling between the Standard Model and the dark sector
in order to facilitate the fast decay of φ before the BBN
era. However as was argued in [28], the requirement for
such a minimum coupling might be at odds with invisible Higgs decay constraints imposed at LHC and with
constraints from direct search experiments like LUX [44],
since this minimum coupling will lead to a minimum DMnucleon cross section in underground detectors. In this
paper here we show how these problems can be avoided.
We will demonstrate that by coupling φ to neutrinos, we
can still have fast decays of φ in the early universe without leading to violation of the experimental constraints
from invisible Higgs decays or direct DM searches. We
also provide and study a renormalizable theory where
such a model can be realized.
The paper is organized as follows: In section II we
present the Higgs portal and the relevant constraints that
can affect the coupling between the dark sector and the
Standard Model. In section III we show how the constraints can be evaded if we couple our mediator to light
sterile neutrinos, or to active neutrinos. Finally we conclude in section IV.
II.
HIGGS PORTAL PHENOMENOLOGY
A.
The Higgs Portal Model
Consider a scenario in which the dark matter X interacts with a light scalar such that the DM self-scattering
cross section is large on dwarf scales, yet small on cluster
scales. In general, this scalar φ will interact with the SM
Higgs through the scalar potential. In the case of a real
The SIMPlest Miracle
Yonit Hochberg1,2 ,∗ Eric Kuflik3 ,† Hitoshi Murayama1,2,4 ,‡ Tomer Volansky5 ,§ and Jay G. Wacker6,7¶
1
arXiv:1411.3727v1 [hep-ph] 13 Nov 2014
Ernest Orlando Lawrence Berkeley National Laboratory,
University of California, Berkeley, CA 94720, USA
2
Department of Physics, University of California, Berkeley, CA 94720, USA
3
Department of Physics, LEPP, Cornell University, Ithaca NY 14853, USA
4
Kavli Institute for the Physics and Mathematics of the Universe (WPI),
Todai Institutes for Advanced Study, University of Tokyo, Kashiwa 277-8583, Japan
5
Department of Physics, Tel Aviv University, Tel Aviv, Israel
6
Quora, Mountain View, CA 94041 USA and
7
Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA 94305 USA
It has recently been proposed that dark matter could be a thermal relic of 3 → 2 scatterings
in a strongly coupled hidden sector. We present explicit classes of strongly coupled gauge theories
that admit this behavior. These are QCD-like theories of dynamical chiral symmetry breaking,
where the pions play the role of dark matter. The number-changing 3 → 2 process, which sets
the dark matter relic abundance, arises from the Wess-Zumino-Witten term. The theories give an
explicit relationship between the 3 → 2 annihilation rate and the 2 → 2 self-scattering rate, which
alters predictions for structure formation. This is a simple calculable realization of the stronglyinteracting-massive-particle (SIMP) mechanism.
INTRODUCTION
The majority of the matter content of our universe is
in the form of dark matter (DM). An appealing explanation for its measured abundance is that it is a thermal
relic of the early universe. The most well-studied thermal
scenario is that of a weakly-interacting-massive-particle
(WIMP), whose relic abundance is set by 2 → 2 annihilations, typically into Standard Model (SM) particles.
This mechanism predicts dark matter mass of order the
weak scale for coupling of order the weak coupling.
Ref. [1] proposed a new paradigm for achieving thermal
relic dark matter. The requisite features of the mechanism are the following:
• The dark matter relic abundance is set thermally
by the freeze-out of a 3 → 2 process that reduces
the number of dark matter particles within the dark
sector.
• At the time of freeze-out, dark matter is in thermal
equilibrium with the SM.
This setup, termed the strongly-interacting-massiveparticle (SIMP) mechanism, robustly predicts light dark
matter with mass in the MeV to GeV range, with strong
self-interactions. Annihilations into SM particles are subdominant during freeze-out, but DM scattering off the
SM bath is fast enough to maintain kinetic equilibrium
between the dark and visible sectors. The strongly interacting hidden sector is expected to contribute to DM
self-scattering cross-sections that are relevant for structure formation.
In what follows, we find explicit strongly coupled realizations for the hidden sector that admit the 3 → 2
process of the SIMP mechanism. Explicit viable realizations for the mediation mechanism between the dark and
visible sectors exist, and will be presented in detail in a
forthcoming publication [2].
THE SIMPLEST REALIZATION
In Ref. [1], a weakly coupled toy model which incorporates the SIMP mechanism and leads to stable dark
matter was presented. Here we present three classes of
strongly coupled gauge theories that realize the SIMP
mechanism. The basic idea is as follows. We use the 5point interaction term present in theories of chiral symmetry breaking, first discovered by Wess and Zumino [3]
and later studied by Witten [4, 5], as the source of the
3 → 2 interactions. This term in massless QCD describes the low energy limit of two kaons annihilating
into three pions. In a given theory, the existence of the
Wess-Zumino-Witten (WZW) term is dictated by a topological condition on the symmetry-breaking pattern; for
coset spaces with non-trivial fifth homotopy groups, the
WZW term is non-vanishing. This 5-point interaction
then generates the 3 → 2 freeze-out process. In what
follows, we demonstrate this explicitly.
We first consider an Sp(Nc ) gauge theory with 2Nf
Weyl fermions in the fundamental Nc -dimensional representation (with the number of colors Nc even). In the
massless limit the UV description takes a simple form
1 a µνa
F
+ q¯i i6Dqi ,
LSIMP = − Fµν
4
i = 1, . . . 2Nf ,
(1)
which admits a global SU(2Nf ) symmetry among the
Weyl fermions qi . It is believed that this model, for moderately small Nf in the asymptotically free range, leads
to chiral symmetry breaking with the order parameter
hqi qj i = µ3 Jij ,
(2)
IPMU14-0335
Chaotic Inflation from Nonlinear Sigma Models in Supergravity
Simeon Hellerman,1, ∗ John Kehayias,1, 2, † and Tsutomu T. Yanagida1, ‡
arXiv:1411.3720v1 [hep-ph] 13 Nov 2014
1
Kavli Institute for the Physics and Mathematics of the Universe (WPI)
Todai Institutes for Advanced Study, The University of Tokyo
Kashiwa, Chiba 277-8582, Japan
2
Department of Physics and Astronomy, Vanderbilt University
Nashville, TN 37235, United States
We present a common solution to the puzzles of the light Higgs or quark masses and the need for a
shift symmetry and large field values in high scale chaotic inflation. One way to protect, for example,
the Higgs from a large supersymmetric mass term is if it is the Nambu-Goldstone boson (NGB) of
a nonlinear sigma model. However, it is well known that nonlinear sigma models (NLSMs) with
nontrivial K¨
ahler transformations are problematic to couple to supergravity. An additional field
is necessary to make the K¨
ahler potential of the NLSM invariant in supergravity. This field must
have a shift symmetry — making it a candidate for the inflaton (or axion). We give an explicit
example of such a model for the coset space SU (3)/SU (2) × U (1), with the Higgs as the NGB,
including breaking the inflaton’s shift symmetry and producing a chaotic inflation potential. This
construction can also be applied to other models, such as one based on E7 /SO(10) × U (1) × U (1)
which incorporates the first two generations of (light) quarks as the Nambu-Goldstone multiplets,
and has an axion in addition to the inflaton. Along the way we clarify and connect previous work
on understanding NLSMs in supergravity and the origin of the extra field (which is the inflaton
here), including a connection to Witten-Bagger quantization. This framework has wide applications
to model building; a light particle from a NLSM requires, in supergravity, exactly the structure for
chaotic inflaton or an axion.
I.
INTRODUCTION AND MOTIVATION
Over the past two years there have been several exciting experimental results, which both confirm theories
developed long before as well as challenge us to better
understand their origin. The discovery of the Higgs boson [1] brings renewed attention to the issue of the apparent lightness of the Higgs mass compared to any UV
scale, like the Planck mass. The Higgs is not the only
light field we are puzzled over; the lightness (smallness
of the Yukawa couplings) of the first two generations of
quarks is a longstanding question. More recently, there
has been much discussion on the possible discovery of
B-modes in the CMB by BICEP2 [2], but which may
be due to dust [3] rather than primordial gravitational
waves. However, a large value for the tensor to scalar
ratio, r ∼ 0.1, is still possible. Such a value, or more
generally any motivations of models for high scale or
large field inflation like chaotic inflation [4], raises the
question of how to control higher dimensional operators
which will not be suppressed in the inflaton potential. In
these models, where do such large field values (of order
or greater than the Planck scale) come from, and how
are such models consistent?
There are several ways to address these problems, although it is not at all obvious that they could be closely
related. Consider first the Higgs mass, which can be
generated by a supersymmetric mass term. One requires
∗
†
‡
[email protected]
[email protected]
[email protected]
some way to either generate a mass much smaller than
the supersymmetry scale, or else forbid this operator. If
the Higgs is a Nambu-Goldstone boson (NGB) of a G/H
nonlinear sigma model (NLSM) [5], this would do both of
these things: a NGB is massless at first approximation,
and cannot have such a mass term. The Higgs mass is
then protected until we introduce operators which break
G/H. More generally, we can think of any light particle,
such as the first two generations of quarks, as a possible
NGB (or fermion partner under supersymmetry) from a
NLSM.
However, as soon as we consider local supersymmetry,
we run into well known problems for coupling a NLSM to
supergravity [6]. The reason is that the K¨ahler potential
has a nontrivial transformation,
K(Φ, Φ† ) → K(Φ, Φ† ) + g(Φ) + g † (Φ† ),
(1)
with g a holomorphic function. Such functions have no
effect in global supersymmetry when integrated over all
of superspace, but in local supersymmetry they do not
disappear. Here, too, there are several solutions which
have been studied in the past [7, 8] (see also [9] and [10]
for earlier work). Generally one must consider a noncompact NLSM, G0 /H, which can be coupled to supergravity. The extension of the original compact manifold
necessarily contains a (at least one) new chiral superfield
Z. It may be surprising that this field must appear in
the K¨ahler potential as Z + Z † , possessing a shift symmetry. In special cases, as in Witten-Bagger models [6],
the manifold can be compact and does not require extra
fields (instead there is the quantization condition of the
K¨ahler form), and we will discuss how these two cases
may possibly be connected.
Ballistic protons in incoherent exclusive vector meson production as a measure of rare
parton fluctuations at an Electron-Ion Collider
T. Lappi,1, 2 H. M¨antysaari,1 and R. Venugopalan3
1
arXiv:1411.0887v1 [hep-ph] 4 Nov 2014
Department of Physics, University of Jyv¨
askyl¨
a,
P.O. Box 35, 40014 University of Jyv¨
askyl¨
a, Finland
2
Helsinki Institute of Physics, P.O. Box 64, 00014 University of Helsinki, Finland
3
Bldg. 510A, Physics Department, Brookhaven National Laboratory, Upton, NY 11973, USA
We argue that the proton multiplicities measured in Roman pot detectors at an electron ion
collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent
diffraction probes the fluctuations in the interaction strengths of multi-parton Fock states in the
nuclear wavefunctions. In particular, the saturation scale that characterizes this multi-parton dynamics is significantly larger in central events relative to minimum bias events. As an application,
we study the centrality dependence of incoherent diffractive vector meson production. We identify
an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and
insensitive to details of the model.
PACS numbers: 13.60.-r,24.85.+p
Introduction Very high multiplicity events in protonproton (p+p) and proton/deuteron-nucleus (p/d+A) collisions at LHC and RHIC have revealed that the structure
of such events is more complex and interesting than previously imagined [1–4]. In particular, interpreting the results of these experiments requires a deeper understanding of event-by-event multi-parton spatial fluctuations in
protons and nuclei [5–9]. Incoherent diffraction in deeply
inelastic scattering (DIS) of electrons off nuclei (e+A collisions) has been long understood as having the potential
to provide insight into event-by-event fluctuations in the
spatial structure of nuclei. A significant advantage of
e+A collisions relative to p+A collisions is that the former is insensitive to the final state interactions that, in
the latter, can complicate the extraction of the spatial
parton structure of the proton and the nucleus.
Insight into rare spatial configurations can be provided
by triggering on central incoherent diffractive events in
e+A collisions. In diffractive events, no net color charge
is exchanged between the fragmentation region of the nucleus and that of the electromagnetic current exciting the
nucleus: a rapidity gap is formed between the two fragmentation regions. Coherent diffraction corresponds to
the case where the nucleus remains fully intact; in incoherent diffraction, the pT kick given to the nucleus is
large enough to break it up, but the rapidity gap is preserved. While the coherent cross section measures the
average spatial distribution of gluons, the fluctuations
are probed by incoherent scattering [10].
For incoherent diffractive events in a collider geometry, such as at a future Electron-Ion Collider (EIC) facility [11], one can distinguish between so-called ballistic
nucleons and evaporation nucleons. Ballistic nucleons are
produced when a nucleon in the nucleus receives a large
longitudinal/transverse momentum kick from the projectile. This nucleon can scatter off other nucleons in the
nucleus on its path out. Evaporation nucleons, on the
Figure 1: Diffractive DIS kinematics.
other hand, are produced when the nucleus is excited as
a whole, causing it to evaporate nucleons according to a
thermal spectrum in the rest frame of the nucleus.
In this work, we will argue that ballistic protons could
be used experimentally as a measure of centrality in incoherent diffractive e+A collisions. These, unlike evaporation nucleons (or ballistic neutrons), can be measured in
forward “Roman pot” detectors located in the beam pipe
outside the main detector. In central events, the number
of these recoil protons should increase. Since we expect
the saturation scale Qs in nuclei in central events to be
enhanced relative to minimum bias events, this opens up
the possibility to select large Qs events in nuclear DIS by
measuring exclusive final states in the central detector in
coincidence with recoil protons from the nucleus in the
Roman pots. Further, the dependence of the results on
kinematic invariants in the scattering shows distinct patterns that make these triggered measurements a sensitive
test of the multi-parton dynamics of gluon saturation.
Kinematics of diffraction at an EIC We will consider
the DIS process e(`) + A(P ) → l0 (`0 ) + A0 (P 0 ) + J/Ψ(V )