The study of monocrystalline silicon neutron beam window for CSNS
Zhou Liang (周良)1,2;1) Qu Hua-Min (屈化民)1
1
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
Abstract: The monocrystalline silicon neutron beam window is one of the key components of neutron spectrometers .Monocrystalline silicon is a
brittle material and its strength is not constant but is consistent with the Weibull distribution. The window is designed not simply through the average
strength, but according to the survival rate. Bending deformation is the main form of the window, so dangerous parts of the neutron beam window is
stress-linearized to the combination of membrane stress and bending stress. According to the Weibull distribution of bending strength of
monocrystalline silicon, finally the optimized neutron beam window is 1.5mm thick and its survival rate is 0.9994; it meets both physical
requirements and the mechanical strength.
Key words: neutron beam window, silicon, China Spallation Neutron Source, modal analysis, brittle materials, neutron spectrometers
PACS: 29.25.Dz, 46.50. +a
1 Introduction
and 0.5mm in thickness. The basic mechanical properties
For China Spallation Neutron Source (CSNS),
neutrons move through every place either in a vacuum
of monocrystalline silicon [2] are showed in tabel1.
Table 1 the basic mechanical properties of monocrystalline silicon
environment, or in special atmosphere, such as helium.
Almost neutron spectrometers have neutron beam
Features
Parameters
Density（293K）
2.327g/cm3
Lattice constant（293K）
541.962pm
spectrometers generally use three kinds of materials for
Knoop hardness
9.5-11.5GPa
beam windows: monocrystalline silicon, sapphire and
Elastic coefficient
windows that are indoors or outdoors for neutrons
[1]
.
Neutron beam window is one of the key components; it
can make neutrons move through with enough loss and
little neutron background. The international neutron
C11=1.6564e11Pa
aluminum alloy. From the physical point of view, silicon
C12=0.6394e11Pa
is the best material and neutron beam window is as thin as
possible; but silicon is a brittle material and neutron beam
C44=0.79514e11Pa
window also meets enough mechanical strength to
Shear strength
240MPa
Tensile strength
350MPa
is the urgent need for all neutron spectrometers.
Compressive strength
950MPa
2 Problems in the development
Bending strength
300-1000 MPa
withstand the pressure, so it is as thick as possible. The
development of neutron beam windows that meet the
physical requirements and satisfy the mechanical strength
Young's modulus
E[100]=1.30e5MPa
The prototype neutron beam window is made from
monocrystalline silicon and has sizes: 40mm in diameter
E[110]=1.68e5MPa
E[111]=1.87e5MPa
1）
Email: [email protected] Preprint typeset in JINST style - HYPER VERSION
arXiv:1411.5990v1 [physics.ins-det] 21 Nov 2014
Radiation experience with the CMS pixel detector
Viktor Veszpremi for the CMS Collaborationa∗
a Wigner
Research Centre for Physics,
1525 Budapest, P.O.Box 49, Hungary
E-mail: [email protected]
A BSTRACT: The CMS pixel detector is the innermost component of the CMS tracker occupying
the region around the centre of CMS, where the LHC beams are crossed, between 4.3 cm and
30 cm in radius and 46.5 cm along the beam axis. It operates in a high-occupancy and highradiation environment created by particle collisions. Studies of radiation damage effects to the
sensors were performed throughout the first running period of the LHC. Leakage current, depletion
voltage, pixel read-out thresholds, and hit finding efficiencies were monitored as functions of the
increasing particle fluence. The methods and results of these measurements will be described
together with their implications to detector operation as well as to performance parameters in offline
hit reconstruction.
K EYWORDS : LHC; CMS; pixel detector, radiation damage.
∗ Supported
by the Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences and the Hungarian
Scientific Research Fund under contract number OTKA NK 109703.
Cosmogenic activation of a natural tellurium target
V. Lozzaa,∗, J. Petzoldta,1
a Institut
f¨ur Kern und Teilchenphysik, Technische Universit¨at Dresden, Zellescher Weg 19, 01069 Dresden, Germany
Abstract
arXiv:1411.5947v1 [physics.ins-det] 21 Nov 2014
130
Te is one of the candidates for the search for neutrinoless double beta decay. It is currently planned to be used in two experiments:
CUORE and SNO+. In the CUORE experiment TeO2 crystals cooled at cryogenic temperatures will be used. In the SNO+
experiment nat Te will be deployed up to 0.3% loading in the liquid scintillator volume. A possible background for the signal
searched for, are the high Q-value, long-lived isotopes, produced by cosmogenic neutron and proton spallation reaction on the target
material. A total of 18 isotopes with Q-value larger than 2 MeV and T1/2 >20 days have been identified as potential backgrounds.
In addition low Q-value, high rate isotopes can be problematic due to pile-up effects, specially in liquid scintillator based detectors.
Production rates have been calculated using the ACTIVIA program, the TENDL library, and the cosmogenic neutron and proton flux
parametrization at sea level from Armstrong and Gehrels for both long and short lived isotopes. The obtained values for the cross
sections are compared with the existing experimental data and calculations. Good agreement has been generally found. The results
have been applied to the SNO+ experiment for one year of exposure at sea level. Two possible cases have been considered: a two
years of cooling down period deep underground, or a first purification on surface and 6 months of cooling down deep underground.
Deep underground activation at the SNOLAB location has been considered.
Keywords: cosmogenic activation, double beta decay, cosmic flux, cross section, production rates, natural tellurium
1. Introduction
The neutrino was introduced for the first time by Pauli in
1930 as a solution for the beta-decay spectrum. Initially considered as a massless particle, during the period from 1990 to
2006 especially the SNO [1] and the SuperK [2] oscillation experiments proved that neutrinos change their flavor when traveling from the source to the detector. This property was already known in the quark sector and happens only if the particles involved do have mass. The existence of massive neutrinos
has been introduced within extensions of the Standard Model.
Two types of neutrino masses are allowed, the Dirac and the
Majorana ones. In the Majorana case neutrinos and their antiparticles are the same.
The investigation of the neutrino’s nature is one of the most
active fields in modern neutrino physics. The search of the Majorana nature of neutrinos is done in the Double-Beta-Decay
(DBD) experiments [3]. The DBD is a nuclear process where
the Z number changes by 2 units while the atomic mass, A, does
not change. It happens only if the single beta decay transition
is forbidden or strongly suppressed. If neutrinos are Majorana
particles, the decay can proceed without the emission of the 2
neutrinos. The result is the presence of a peak at the Q-value of
the reaction in the sum energy spectrum of the two electrons.
There are about 35 candidates nuclei for the DBD searches. The
quantity extracted from the number of events in the peak is the
∗ Corresponding
author: V. Lozza
Email address: [email protected] (V. Lozza)
1 Present address: OncoRay, National Center for Radiation Research in Oncology, 01307 Dresden, Germany
half-life of the decay. The expected value for the neutrinoless
double beta decay half life is larger than 1025 years. To search
for such a rare event a large mass (volume), a very low background environment and a good knowledge of the backgrounds
in the detector are necessary.
A possible source of background is the activation of the candidate material through spallation reaction induced by cosmogenic neutrons and protons during handling on surface. A study
of the cosmogenic-induced isotopes has been done for several
double beta decay experiments, like GERDA [4] and CUORE
[5], in order to define the maximum allowed exposure on surface, the necessary shielding during transportation, the necessary purification factors, and the cooling down time underground (UG) to reduce the cosmogenic background to a negligible level.
In this article the studies are focused on a natural tellurium
target. 130 Te is the candidate nucleus chosen by the CUORE
and the SNO+ collaborations for the search for the neutrinoless double beta decay. 130 Te has a high natural isotopic abundance of 34.08% and a relative high Q-value of 2.53 MeV. The
CUORE collaboration will use tellurium in form of crystals
(TeO2 ) cooled at cryogenic temperatures. The energy resolution of the crystals is nearly 5–7 keV (FWHM) at 2.53 MeV [6].
The cosmogenic-induced isotopes identified as possible background by the collaboration are 60 Co, 124 Sb and 110m Ag. The
calculated exposure time at sea level for the Te crystals in [5]
was 4 months, followed by 2 years of storage underground.
The SNO+ experiment will use a tellurium loaded liquid scintillator to search for neutrinoless double beta decay. The tellurium
acid (Te(OH)6 ) is dissolved in the liquid scintillator using water
Comparing readout strategies to directly detect dark matter
J. Billard∗
arXiv:1411.5946v1 [physics.ins-det] 21 Nov 2014
IPNL, Universit´e de Lyon, Universit´e Lyon 1, CNRS/IN2P3,
4 rue E. Fermi 69622 Villeurbanne cedex, France
Over the past decades, several ideas and technologies have been developed to directly detect WIMP
from the galactic halo. All these detection strategies share the common goal of discriminating a
WIMP signal from the residual backgrounds. By directly detecting WIMPs, one can measure some
or all of the observables associated to each nuclear recoil candidates, such as their energy and
direction. In this study, we compare and examine the discovery potentials of each readout strategies
from counting only (bubble chambers) to directional detectors (Time Projection Chambers) with
1d-, 2d-, and 3d-sensitivity. Using a profile likelihood analysis, we show that, in the case of a large
and irreducible background contamination characterized by an energy distribution similar to the
expected WIMP signal, directional information can improve the sensitivity of the experiment by
several orders of magnitude. We also found that 1d directional detection is only less effective than
a full 3d directional sensitivity by about a factor of 3, or 10 if we assume no sense recognition, still
improving by a factor of 2 or more if only the energy of the events is being measured.
PACS numbers: 95.35.+d; 95.85.Pw
I.
INTRODUCTION
An ever increasing body of evidence supports the
existence of Cold Dark Matter (CDM) as a major
contribution to the matter budget of the Universe. On
the largest scale, cosmological measurements [1] tightly
constrain the CDM relic density whereas on a local scale,
measurements of the rotation curves of spiral galaxies,
including the Milky Way, indicates that they should
be embedded in a Dark Matter halo [2, 3]. A leading
candidate for this dark matter is a yet-to-be-discovered
weakly interacting massive particle (WIMP) which
could directly interact with detectors based on Earth
leading to keV-scale nuclear recoils. Direct detection
experiments are now probing well-motivated extensions
to the Standard Model which naturally predict dark
matter candidates [4–6]. However, as dark matter
detectors are rapidly improving in sensitivity [7], they
will encounter the neutrino background, at which point
Solar, atmospheric, and diffuse supernova neutrinos will
interfere with a potential dark matter signal [8–12].
Moreover, the recent controversy in the low-mass WIMP
region ∼ O(10 GeV/c2 ), where several dark matter hints
are inconsistents with null results [13], highlights the
need for additional discrimination power between WIMP
events and backgrounds in order to clearly authentify a
genuine WIMP signal.
Several ideas and detector readouts have been developed over the past decades that allows to detect keVscale nuclear recoils as produced by O(10-1000) GeV/c2
WIMPs. As of today, the main categories of experiments
are: cryogenic semiconductor detectors [14–17], single(liquid) and dual-phase (liquid/gas) Argon or Xenon
∗ Electronic
address: [email protected]
Time Projection Chambers (TPC) [18–21], bubble chambers operating such that they are only sensitive to nuclear
recoils [22–24], and low-pressure gaseous TPC aiming at
measuring both the energy and the track of the recoiling
nucleus [25–28]. Each of these detection techniques share
the common goal of discriminating a potential WIMP signal from residual backgrounds by either comparing the
different amount of energy released in scintillation, ionization and heat, and/or using pulse shape discrimination. Depending on the readout strategy being considered, direct detection experiments can have access to the
number of WIMP candidates contained in the data set,
their recoil energies and directions. In this study we want
to compare the different readout strategies by evaluating
their discovery potential in various experimental conditions, especially when the data set is contaminated with
some irreducible backgrounds.
This paper is organized as follows. In Sec. II, we briefly
review the dark matter rate calculations with a particular
emphasis on the directionality of WIMP induced events
in both the galactic and detector-based coordinates. We
then discuss the analysis methodology used to compare
the discovery reach associated to each readout strategies
in Sec. III and discuss the detector configurations used in
our simulations in Sec. IV. Finally, we present our results
in Sec. V and conclude in the last section.
II.
DIRECT DETECTION OF DARK MATTER
Direct dark matter detection aims at detecting elastic
scattering between a WIMP from the galactic halo and
the detector material. The differential event rate as a
function of both the recoil energy (Er ) and direction in
the lab frame (Ωr ) is given by
d2 R
ρ0 σ0
= MT ×
F 2 (Er )fˆ(vmin , qˆ; t),
dEr dΩr
4πmχ µ2N
(1)
Measurement of Leakage Neutron Spectra for Tungsten with D-T
Neutrons and Validation of Evaluated Nuclear Data
S. Zhanga 1,2 , Z. Chen 1,*, Y. Nie3 , R. Wada 1 , X. Ruan 3 , R. Han 1 , X. Liu 1,2 , W. Lin 1,2 , J. Liu 1 ,
F. Shi 1 , P. Ren 1,2 , G. Tian 1,2 , F. Luo 1 , J. Ren 3 , J. Bao 3
1
Institute of Modern Physics, Chinese Academy of Sciences, Gansu, Lanzhou 730000, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
3
Science and Technology on Nuclear Data Laboratory, China Institute of Atomic Energy, Beijing 102413, China
*
Corresponding author. E-mail address: [email protected]
Abstract: Integral neutronics experiments have been investigated at Institute of Modern Physics,
Chinese Academy of Sciences (IMP, CAS) in order to validate evaluated nuclear data related to the
design of Chinese Initiative Accelerator Driven Systems (CIADS). In present paper, the accuracy of
evaluated nuclear data for Tungsten has been examined by comparing measured leakage neutron
spectra with calculated ones. Leakage neutron spectra from the irradiation of D-T neutrons on
Tungsten slab sample were experimentally measured at 60˚ and 120˚ by using a time-of-flight method.
Theoretical calculations are carried out by Monte Carlo neutron transport code MCNP-4C with
evaluated nuclear data of the ADS-2.0, ENDF/B-VII.0, ENDF/B-VII.1, JENDL-4.0 and CENDL-3.1
libraries. From the comparisons, it is found that the calculations with ADS-2.0 and ENDF/B-VII.1
give good agreements with the experiments in the whole energy regions at 60˚, while a large
discrepancy is observed at 120˚ in the elastic scattering peak, caused by a slight difference in the
oscillation pattern of the elastic angular distribution at angles larger than 20˚. However, the
calculated spectra using data from ENDF/B-VII.0, JENDL-4.0 and CENDL-3.1 libraries showed
larger discrepancies with the measured ones, especially around 8.5-13.5 MeV. Further studies are
presented for these disagreements.
Key words: Integral experiment, Leakage neutron spectra, Nuclear data library, Tungsten, CIADS
1. Introduction
China has started to develop the Chinese Initiative Accelerator Driven Systems (CIADS) project
and is now underway vigorously. This project mainly aims for high radioactive nuclear waste
transmutation, fuel breeding and clean energy production. In the design of CIADS, high intensity of
~1GeV proton beam bombards on heavy metal spallation target inside the subcritical reactor, and
provides external neutron source for the subcritical reactor. The combination of evaluated nuclear
data with a Monte Carlo transportation code like MCNP [1] is widely utilized for designing such
kind of nuclear engineering facilities. However, the transportation codes and evaluated nuclear data
used need to be validated through integral experiments [2-9].
Rare exclusive decays of the Z-boson revisited
Ting-Chung Huang∗
Department of Physics & Astronomy,
arXiv:1411.5924v1 [hep-ph] 21 Nov 2014
Northwestern University, Evanston, IL 60201,USA
Frank Petriello†
Department of Physics & Astronomy,
Northwestern University, Evanston, IL 60201,USA and
High Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439,USA
(Dated: November 24, 2014)
Abstract
The realization that first- and second-generation Yukawa couplings can be probed by decays
of the Higgs boson to a meson in association with a photon has renewed interest in such rare
exclusive decays. We present here a detailed study of the rare Z-boson processes Z → J/ψ + γ,
Z → Υ+γ, and Z → φ+γ that can serve as benchmarks for the analogous Higgs-boson decays. We
include both direct-production and fragmentation contributions to these decays, and consider the
leading QCD corrections and the relativistic corrections to the J/ψ and Υ processes. We present
numerical predictions for the branching ratios that include a careful accounting of the theoretical
uncertainties.
∗
[email protected]
†
[email protected]
1
Optimization parameter design for proton irradiation accelerator
AN Yu-Wen (安宇文)*1,2, JI Hong-Fei(纪红飞)3, WANG Sheng (王生)1,2, XU Shou-Yan(许守彦)1,2
1
China Spallation Neutron Source (CSNS), Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS)，
Dongguan 523803, China
2
Dongguan Institute of Neutron Science (DINS), Dongguan 523808, China
3
Institute of High Energy Physics (IHEP), Beijing 100049, China
The proton irradiation accelerator is widely founded for industry application, and should be designed as
compact, reliable, and easy operate. A 10 MeV proton beam is designed to be injected into the slow
circulation ring with the repetition rate of 0.5 Hz for accumulation and acceleration, and then the beam with
the energy of 300MeV will be slowly extracted by third order resonance method. For getting a higher
intensity and more uniform beam, the height of the injection bump is carefully optimised during the injection
period. Besides, in order to make the extracted beam with a more uniform distribution, a RF Knock-out
method is adopted, and the RF kicker’s amplitude is well optimised.
Proton irradiation accelerator, injection bump, RF knock-out
PACS: 41.85.ar, 29.27.ac
1
Introduction
The basic design of a compact proton accelerator
system for irradiation accelerator is described. The system
consists of a 50KeV H− ion source, a 10 MeV tandem
accelerator, and a 300MeV slow cycling synchrotron. When
H− beam travels along the tandem, the electrons of the H− are
scraped through Argon gas in low pressure, and then the
proton beam is transported through beam line. The DC
mode proton beam is injected into the ring through a
two-bump structure with the beam current of 100uA. When
the energy of the proton beam reaches 300MeV, the beam
will be slowly extracted by third order resonance method.
The main parameters of the irradiation proton accelerators
are listed in Table 1 [1].
Table 1: Main parameters of irradiation proton accelerator
Parameters
Units
Values
Ring circumference
m
33.6
Inj. Energy
MeV
10
Ext. Energy
MeV
300
Nominal Tunes(H/V)
in ring
Repetition rate
Beam emmittance in
ring (99%)
π mm-mrad
25/25
Beam emmittance for
one inj. pulse (99%)
π mm-mrad
6.83
Proton Number in
ring
5*109
Momentum deviation
5*10-4
Inj. scheme
Multi-turn injection
Ext. scheme
Slow extraction
(RFKO)
Third order resonance method is a common technique
for better control of the extracted beam characters. When
the horizontal tune of the beam is near n ± 1/ 3 (n is a
random integer), particles far away for the beam core may
become unstable, that is because the sextuples in the ring
establish a limited stable area in the shape of triangle. In
order to control the extracted beam more precisely, a RF
knock-out method is adopted to make the particles
amplitude growth beyond the triangle. The RF kicker’s
amplitude is carefully modified during the period of the
extraction to make the extraction beam more flatten.
1.70/1.20
2
Hz
*Corresponding author (email: [email protected])
0.5
Optimisation of the injection bump height
decrease pattern
The Lattice of the proton irradiation synchrotron is
designed with two super-period, and each one super-period
consists of two FODO structure. 8 dipoles with 45 degrees
Nuclear Electric Dipole Moments
in Chiral Effective Field Theory
arXiv:1411.5804v1 [hep-ph] 21 Nov 2014
J. Bsaisoua , J. de Vriesa , C. Hanharta,b , S. Liebiga ,
Ulf-G. Meißnera,b,c,d , D. Minossia , A. Noggaa,b , and A. Wirzbaa,b
a
b
Institute for Advanced Simulation, Institut f¨
ur Kernphysik, and J¨
ulich Center for
Hadron Physics, Forschungszentrum J¨
ulich, D-52425 J¨
ulich, Germany
JARA – Forces and Matter Experiments, Forschungszentrum J¨
ulich, D-52425 J¨
ulich,
Germany
c
JARA – High Performance Computing, Forschungszentrum J¨
ulich, D-52425 J¨
ulich,
Germany
d
Helmholtz-Institut f¨
ur Strahlen- und Kernphysik and Bethe Center for Theoretical
Physics, Universit¨at Bonn, D-53115 Bonn, Germany
Abstract
We provide the first consistent and complete calculation of the electric dipole moments
of the deuteron, helion, and triton in the framework of chiral effective field theory. The
CP-conserving and CP-violating interactions are treated on equal footing and we consider
CP-violating one-, two-, and three-nucleon operators up to next-to-leading-order in the chiral
power counting. In particular, we calculate for the first time EDM contributions induced by
the CP-violating three-pion operator. We find that effects of CP-violating nucleon-nucleon
contact interactions are larger than those found in previous studies based on phenomenological models for the CP-conserving nucleon-nucleon interactions. Our results are modelindependent and can be used to test various scenarios of CP violation. As examples, we study
the implications of our results on the QCD θ-term and the minimal left-right symmetric
model.
Missing Top Properties
arXiv:1411.5697v1 [hep-ph] 20 Nov 2014
J. A. Aguilar-Saavedra
Departamento de F´ısica Te´
orica y del Cosmos, Universidad de Granada, E-18071 Granada
E-mail: [email protected]
Abstract. We discuss top polarisation observables at the Tevatron and the LHC with special
attention to some that have not been measured and provide new, independent information about
the top polarisation.
1. Introduction
In 2011, the measurement by the CDF Collaboration of an anomalous forward-backward (FB)
asymmetry in tt¯ production at the Tevatron drew a great attention into top quark physics
and, in particular, it fostered the theoretical studies of top quark properties (see [1] for a
review and references). The deviations in the FB asymmetry are smaller in some of the latest
measurements using the full Tevatron dataset. But, irrespectively of the reason behind these
deviations—new physics, systematic bias or statistical fluctuations—the related developments
are very interesting on their own. Here we will focus on top polarisation observables, which
provide a good opportunity to detect elusive new physics in top pair and single top production.
We will begin by setting the theoretical framework, and then proceed to discuss some polarisation
observables for the Tevatron and for the Large Hadron Collider (LHC).
2. Theoretical framework
The top quark is not a stable particle but it decays mainly into a W boson and a b quark,
with a predicted average life of 5 × 10−25 s. For a process in which a top quark is produced
and subsequently decays into W b, for example pp → tX → W bX (with X denoting possible
additional particles), the amplitude contains an s-channel top propagator. Since the top quark
width Γt is small compared to its mass mt , one can approximate the propagator as [2]
X
6 pt + mt
π
2
2
→
δ(p
−
m
)
u(pt , λ)¯
u(pt , λ) ,
t
t
Γt mt
p2t − m2t + iΓt mt
λ
(1)
in standard notation [3], P
with pt the top quark momentum and λ its helicity. Then, the amplitude
is decomposed as M ∝ λ Aλ × Bλ , a sum of production (Aλ ) × decay (Bλ ) factors, summed
over the possible top helicities. Taking the modulus
squared of the amplitude, the differential
P
cross section can be written as dσ ∝ |M|2 ∝ λ,λ0 Aλ Bλ A∗λ0 Bλ∗0 . The product A∗λ0 Aλ can be
identified with the top spin density matrix, which for a spin-1/2 particle can be written in
general as
1
1 + Pz Px − iPy
,
(2)
ρ=
2 Px + iPy 1 − Pz
Could the near–threshold XY Z states be simply kinematic effects?
Feng-Kun Guo1∗ , Christoph Hanhart2† , Qian Wang2‡ , Qiang Zhao3§
arXiv:1411.5584v1 [hep-ph] 20 Nov 2014
3
1
Helmholtz-Institut f¨
ur Strahlen- und Kernphysik and Bethe Center
for Theoretical Physics, Universit¨
at Bonn, D-53115 Bonn, Germany
2
Institut f¨
ur Kernphysik and Institute for Advanced Simulation,
Forschungszentrum J¨
ulich, D–52425 J¨
ulich, Germany
Institute of High Energy Physics and Theoretical Physics Center for Science Facilities,
Chinese Academy of Sciences, Beijing 100049, China
(Dated: November 21, 2014)
We demonstrate that the spectacular structures discovered recently in various experiments and
named as X, Y and Z states cannot be purely kinematic effects. Their existence necessarily calls
for nearby poles in the S–matrix and they therefore qualify as states.
PACS numbers: 14.40.Rt, 13.75.Lb, 13.20.Gd
In recent years various narrow (widths from well below 100 MeV down to values even below 1 MeV) peaks
were discovered both in the charmonium as well as in
the bottomonium mass range that do not fit into the
so far very successful quark model. For instance, the
most prominent ones include X(3872) [1], Zc (3900) [2–
4], Zc (4020) [5–8], Zb (10610) and Zb (10650) [9], which
¯ ∗ , DD
¯ ∗ , D∗ D
¯ ∗, BB
¯ ∗ and B ∗ B
¯∗
are located close to DD
thresholds in relative S–waves, respectively. Apart from
other interpretations, such as hadro-quarkonia [10, 11],
hybrids [12–14], and tetraquarks [15, 16] (for recent reviews we refer to Refs. [17, 18]), due to their proximity to
the thresholds these five states were proposed to be of a
molecular nature [19–37]. As an alternative explanation
various groups conclude from the mentioned proximity of
the states to the thresholds that the structures are simply kinematical effects [38–45] that necessarily occur near
every S-wave threshold. Especially, it has been claimed
that the structures are not related to a pole in the S–
matrix and therefore should not be interpreted as states.
In this letter we show that the latter statement is based
on calculations performed within an inconsistent formalism. In particular, we demonstrate that, while there is
always a cusp at the opening of an S–wave threshold,
in order to produce peaks as pronounced and narrow
as observed in experiment non-perturbative interactions
amongst the heavy mesons are necessary, and as a consequence, there is to be a near-by pole. Or, formulated
the other way around: if one assumes the two–particle
interactions to be perturbative, as it is implicitly done in
Refs. [38–45], the cusp should not appear as a prominent
narrow peak. This statement is probably best illustrated
by the famous K ± → π ± π 0 π 0 data [46]: the cusp that
appears in the π 0 π 0 invariant mass distribution at the
∗ Email
address:
address:
‡ Email address:
§ Email address:
† Email
[email protected]
[email protected]
[email protected]
[email protected]
π
Y
D
D*
π
Y
D
D
D*
D*
(a)
π
Y
(b)
D
D
D
D*
D*
D*
(c)
FIG. 1: The tree-level, one-loop and two-loop Feynman dia¯ ∗.
grams for Y (4260) → πDD
π + π − threshold is a very moderate kink, since the ππ
interactions are sufficiently weak to allow for a perturbative treatment (for a comprehensive theoretical framework and related references we refer to Ref. [47]).
To be concrete, in this paper we demonstrate our argument on the example of an analysis of the existing data on
the Zc (3900), but it should be clear that the reasoning as
such is general and applies to all structures observed very
near S–wave thresholds such as those above-mentioned
XY Z states. To illustrate our point, we here do not aim
for field theoretical rigor but use a very simple separable
interaction for all vertices accompanied by loops regularized with a Gaussian regulator. This regulator will at the
same time control the drop-off of the amplitudes as will
be discussed below. Accordingly, we write for the Lagrangian that produces the tree–level vertices (here and
¯ ∗ for the proper
in what follows we generically write DD
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP/2014-273
2014/11/24
CMS-EXO-12-034
arXiv:1411.6006v1 [hep-ex] 21 Nov 2014
Search for disappearing tracks
in proton-proton collisions
√
at s = 8 TeV
The CMS Collaboration∗
Abstract
A search is presented for long-lived charged particles that decay within the CMS detector and produce the signature of a disappearing track. Disappearing tracks are
identified as those with little or no associated calorimeter energy deposits and with
missing hits in the outer layers of the tracker. The search uses proton-proton collision
√
data recorded at s = 8 TeV that corresponds to an integrated luminosity of 19.5 fb−1 .
The results of the search are interpreted in the context of the anomaly-mediated supersymmetry breaking (AMSB) model. The number of observed events is in agreement with the background expectation, and limits are set on the cross section of direct
electroweak chargino production in terms of the chargino mass and mean proper lifetime. At 95% confidence level, AMSB models with a chargino mass less than 260 GeV,
corresponding to a mean proper lifetime of 0.2 ns, are excluded.
Submitted to the Journal of High Energy Physics
c 2014 CERN for the benefit of the CMS Collaboration. CC-BY-3.0 license
∗ See
Appendix B for the list of collaboration members
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–7
Search for long-lived particles at CMS
Paul Lujan, for the CMS Collaboration
arXiv:1411.5939v1 [hep-ex] 21 Nov 2014
Princeton University, Department of Physics, Princeton NJ 08544
Abstract
The most recent searches for long-lived particles at CMS are presented. Searches for displaced jets, displaced
leptons, displaced stops, and heavy stable charged particles are among those discussed. A variety of models are
constrained by these searches, ranging from hidden valleys to split supersymmetry.
Keywords:
1. Introduction
Many models of new physics predict the existence
of new, long-lived particles, which would appear with
a very distinctive experimental signature. Scenarios in
which these new particles could arise include supersymmetric (SUSY) scenarios such as “split SUSY” [1] or
SUSY with very weak R-parity violation [2], “hidden
valley” models [3], and Z’ models that include longlived neutralinos [4].
The Compact Muon Solenoid (CMS) collaboration [5] has conducted a number of searches for a variety of different experimental signatures and theoretical
models using data collected from proton-proton collisions at the Large Hadron Collider (LHC). This paper
presents an overview of√the results of these searches using 2012 data taken at s = 8 TeV.
There are four analyses discussed here: the first, the
“displaced lepton” analysis [6], searches for long-lived
neutral particles with a lifetime such that they decay
within the CMS detector, but at a significant displacement from the primary event vertex. The decay products of these particles include a pair of either electrons
or muons. The second, the “displaced jets” analysis [7],
considers a similar model, but for the case where the
long-lived particles decay into jets. The third, the “displaced SUSY” analysis [8], considers a model where
stops are pair-produced and decay via e
te
t → bebµ. Finally, the “heavy stable charged particle” (HSCP) analy-
sis [9] searches for particles with a large enough lifetime
that they do not decay inside the CMS detector. These
particles may have a velocity significantly less than c or
a charge not equal to ±e.
2. Displaced leptons
The displaced lepton search is sensitive to a wide
class of models that contain long-lived particles decaying to leptons, but for the context of computing limits,
two specific signal models are considered. In the first, a
non-Standard Model (SM) Higgs decays to a long-lived
spinless boson X (H 0 → XX), which then decays into a
pair of leptons (either X → ee or X → µµ). In the second model, a pair of squarks is produced in the initial
pp collision; each squark then decays into a long-lived
neutralino (e
q → qe
χ0 ). The neutralino then has a Rparity violating decay into a neutrino and two leptons
(e
χ0 → `+ `− ν). Although in these models the long-lived
particles are pair-produced and so we would expect to
observe up to two displaced vertices per event, for maximum generality this search only requires one displaced
vertex to be found.
The data is collected using a pair of triggers, one
for each channel, requiring either two high-energy deposits in the electromagnetic calorimeter or two highmomentum tracks in the muon detector. In both cases,
the tracker information is not used in the trigger, as
SNSN-323-63
November 24, 2014
arXiv:1411.5918v1 [hep-ex] 21 Nov 2014
Measurement of CP violating phase φs and control of penguin
pollution at LHCb
Walaa KANSO
on behalf of the LHCb collaboration
CPPM, Aix-Marseille Universit´e CNRS/IN2P3, Marseille, France
The study of CP violation in Bs0 oscillations is a key measurement
at the LHCb experiment. In this document, we discuss the latest LHCb
results on the CP-violating phase, called φs , using Bs0 → J/ψK − K + and
Bs0 → J/ψπ − π + channels. To conclude on the presence of New Physics in
φs , the estimation of the sub-dominant contributions from the Standard
Model becomes crucial now. We outline a method to estimate the contribution of penguin diagrams in φs . Branching fractions and upper limits
0
0
of B 0 (s) → J/ψKS0 h( )+ h− (h( ) = K, π) modes are presented.
PRESENTED AT
8th International Workshop on the CKM Unitarity Triangle
(CKM 2014)
8-12 September 2014, Vienna, Austria
1
Introduction
The interference between Bs0 mesons decaying directly via b → ccs transitions to CP
eigenstates and those decaying after Bs0 -B 0s oscillations gives rise to a CP violating
phase called φs .
Within the Standard Model, the decay can occur via two main topologies: the
predominant tree topology and the sub-leading penguin diagram. New Physics processes, e.g., new particles contributing to the box diagrams, can modify the value of
φs :
φmeas
= −2βs + ∆φpeng
+ δ NP
s
s
The indirect determination
via global fit to experimental data gives:
?
Vts Vtb
−2βs = 2 arg( Vcs
? ) = −0.0363 ± 0.0013 [7]. The theoretical uncertainty on φs is
Vcb
mainly due to unknown penguin contributions ∆φpeng
. The control of penguin pollus
tion is limited by large theoretical uncertainties. Thus, experimental measurements
are very useful to constrain the contribution of penguin diagrams. Therefore, we
should estimate ∆φpeng
, otherwise we may incorrectly interpret the Standard Model
s
penguin contributions as signs of New Physics. In Section 2, we summarize the measurement of the CP-violating phase φs in Bs0 → J/ψK − K + . In Section 3, we report
on a recent update of the same measurement using Bs0 → J/ψπ − π + . The studies of
penguin pollution in φs and 2β are described in Section 4 and 5 respectively. A recent
0
0
result on the branching ratio of B 0 (s) → J/ψKS0 h( )+ h− (h( ) = K, π) modes is shown
in Section 6.
2
Bs0 → J/ψK −K +
The purpose of this analysis is to mainly measure φs , the decay width difference ∆Γs
and Γs . Bs0 → J/ψ[→ µ+ µ− ]φ[→ K + K − ] is pseudo-scalar decaying into two vector
mesons. The study of this decay requires an angular analysis in order to disentangle
CP-odd/CP-even mixture of the final state. After the statistical background subtraction [3], a fit to decay time (t) and three angles in helicity frame (Ω = θµ , θK , ϕh ) is
performed in six bins of mKK [5]. To account for the detector and selection effects, the
decay time acceptance is taken from real data and the angular acceptance is studied in
the simulated data. The finite decay time resolution is modelled by a single Gaussian
of width Sσt × σt , where σt is the estimated per event decay time uncertainty, and
the scale factor, Sσt , is measured in a sample of prompt J/ψ → µ+ µ− . The effective
resolution is 45 fs for Bs0 → J/ψφ. The Bs0 flavour, at production, is determined by
the combination of the same side kaon tagger and the opposite side taggers, which
gives the overall tagging power: (1 − 2ω)2 = (3.13 ± 0.23)%, where indicates the
tagging efficiency, and ω the mistag rate [14]. Using 1 fb−1 of real data collected in
2011, LHCb obtained:
1
Superallowed 0+ → 0+ nuclear β decays: 2014 critical survey, with precise results for
Vud and CKM Unitarity
J.C. Hardy∗ and I.S. Towner†
arXiv:1411.5987v1 [nucl-ex] 21 Nov 2014
Cyclotron Institute, Texas A&M University, College Station, Texas 77843
(Dated: November 24, 2014)
A new critical survey is presented of all half-life, decay-energy and branching-ratio measurements
related to 20 superallowed 0+ → 0+ β decays. Included are 222 individual measurements of comparable precision obtained from 177 published references. Compared with our last review in 2008,
we have added results from 24 new publications and eliminated 9 references, the results from which
having been superceded by much more precise modern data. We obtain world-average f t-values for
each of the eighteen transitions that have a complete set of data, then apply radiative and isospinsymmetry-breaking corrections to extract “corrected” Ft values. Fourteen of these Ft values now
have a precision of order 0.1% or better. In the process of obtaining these results we carefully evaluate the available calculations of the isospin-symmetry-breaking corrections by testing the extent to
which they lead to Ft values consistent with conservation of the vector current (CVC). Only one set
of calculations satisfactorily meets this condition. The resultant average Ft value, when combined
with the muon liftime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa
(CKM) matrix, Vud = 0.97417 ± 0.00021. The unitarity test on the top row of the matrix becomes
|Vud |2 + |Vus |2 + |Vub |2 = 0.99978 ± 0.00055 if the Particle Data Group recommended value for Vus
is used. However, recent lattice QCD calculations, not included yet in the PDG evaluation, have
introduced some inconsistency into kaon-decay measurements of Vus and Vus /Vud . We examine the
impact of these new results on the unitarity test and conclude that there is no evidence of any
statistically significant violation of unitarity. Finally, from the Ft-value data we also set limits on
the possible existence of scalar interactions.
PACS numbers: 23.40.Bw, 12.15.Hh, 12.60.-i
I.
INTRODUCTION
Precise measurements of the beta decay between nuclear analog states of spin, J π = 0+ , and isospin, T = 1,
provide demanding and fundamental tests of the properties of the electroweak interaction. Collectively, these
transitions sensitively probe the conservation of the vector weak current, set tight limits on the presence of
scalar currents and provide the most precise value for
Vud , the up-down quark-mixing element of the CabibboKobayashi-Maskawa (CKM) matrix. This latter result
has become a linchpin in the most demanding available
test of the unitarity of the CKM matrix, a property which
is fundamental to the electroweak standard model.
We have published six previous surveys of 0+ → 0+
superallowed transitions [1–6], the first having appeared
over 40 years ago and the most recent, six years ago.
In each, we published a complete survey of all relevant
nuclear data that pertained to these superallowed transitions and used the results to set limits on the weakinteraction parameters that were important at the time.
Notably, since Vud became the quantity of greatest interest 25 years ago, its value as obtained from our surveys
of superallowed decays has improved by a factor of five
in precision but has never strayed outside of the uncertainties quoted in preceding surveys. This consistency
∗ Electronic
† Electronic
address: [email protected]
address: [email protected]
is testimony to the robustness of what is by now a very
large body of nuclear data.
Since our last survey closed in September 2008, there
has continued to be a great deal of activity in this field,
both in experiment and in theory. And this activity in
honing Vud has been matched by efforts to make similar
improvements in the value of Vus , the second important
element in the top-row unitarity sum. (The third element, Vub , is too small to play a significant role.) Since
the value of Vus has undergone some unexpected changes
in the past decade and has not yet settled at a reliably
stable result, interest in the CKM unitarity test continues
to stimulate work in the field. Since 2008, new measurements relating to 0+ → 0+ superallowed transitions have
appeared in 24 publications, and the new more-precise
results they contain have made 9 of the references accumulated in 2008 entirely obsolete and left 11 more with
some results replaced, in all cases because new values had
uncertainties a factor of ten or more smaller. Altogether
this means that, of the references in this 2014 survey,
about 15% are new and, being among the most precise,
their influence is disproportionately greater than that.
In addition to new measurements, there have also been
important theoretical contributions to the small isospinsymmetry-breaking corrections that must be applied to
the data in order to extract Vud and the values of other
weak-interaction parameters. In the past six years, a
number of different groups have published their results
for these terms, with calculations based upon a variety
of different models. The diversity of results has prompted
development of a test that allows each set of correction
Prepared for submission to JHEP
arXiv:1411.5964v1 [hep-th] 21 Nov 2014
Holographic renormalization and
anisotropic black branes in higher curvature gravity
Viktor Jahnke, Anderson Seigo Misobuchi, and Diego Trancanelli
Institute of Physics, University of S˜
ao Paulo
05314-970 S˜
ao Paulo, Brazil
E-mail: viktor.jahnke, anderson.misobuchi, [email protected]
Abstract: We consider five-dimensional AdS-axion-dilaton gravity with a Gauss-Bonnet
term and find a solution of the equations of motion which corresponds to a black brane
exhibiting a spatial anisotropy, with the source of the anisotropy being an axion field
linear in one of the horizon coordinates. Our solution is static, regular everywhere on and
outside the horizon, and asymptotically AdS. It is analytic and valid in a small anisotropy
expansion, but fully non-perturbative in the Gauss-Bonnet coupling. We discuss various
features of this solution and use it as a gravity dual to a strongly coupled anisotropic
plasma with two independent central charges, a 6= c. In the limit of small Gauss-Bonnet
coupling, we carry out holographic renormalization of the system using (a recursive variant
of) the Hamilton-Jacobi method and derive a generic expression for the boundary stress
tensor, which we later specialize to our solution. Finally, we compute the shear viscosity
to entropy ratios and conductivities of this anisotropic plasma.
Keywords: Gauge-gravity correspondence, Holography and quark-gluon plasmas
SLAC-PUB-16136
Effective field theory interpretation of searches for dark matter annihilation in the
Sun with the IceCube Neutrino Observatory
Jan Blumenthal,1, ∗ Pavel Gretskov,1, † Michael Kr¨amer,2, ‡ and Christopher Wiebusch1, §
1
arXiv:1411.5917v1 [astro-ph.HE] 21 Nov 2014
III. Physikalisches Institut B, RWTH Aachen University, 52056 Aachen, Germany
2
Institute for Theoretical Particle Physics and Cosmology,
RWTH Aachen University, 52056 Aachen, Germany
and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94025, USA
(Dated: November 24, 2014)
We present a model-independent interpretation of searches for dark matter annihilation in the Sun
using an effective field theory approach. We identify a set of effective operators contributing to spindependent scattering of dark matter with protons in the non-relativistic limit and explore simple
new physics models which would give rise to such operators. Using the limits on the spin-dependent
scattering cross-section set by the IceCube collaboration in their search for dark matter annihilation
in the Sun, we derive limits on effective couplings and corresponding masses of mediating particles.
We show that the effective field theory interpretation of the IceCube searches provides constraints
on dark matter complementary to those from relic density observations and searches at the LHC.
Finally, we discuss the impact of astrophysical uncertainties on our results.
PACS numbers: 95.35.+d, 12.60.-i
I.
INTRODUCTION
Since its first discovery by Zwicky in the 1930s [1],
there has been an ever-growing list of observational evidence for the existence of dark matter. These observations led to the understanding that presumably every
galaxy, including our own Milky Way, is surrounded by
a halo of dark matter [2–6]. It became clear, that in order to consolidate this evidence with the Standard Model
of particle physics (SM), which does not include a suitable candidate for dark matter, the SM would have to be
extended. Some of the extensions, like supersymmetry
(SUSY) or axions, deal with more general questions in
particle physics and naturally provide dark matter candidate particles, while other models take a more ad hoc
approach to dark matter (for an extensive list see [7]).
One popular idea is that dark matter could be a stable
weakly interacting massive particle (WIMP) with masses
near the TeV-scale and weak interaction strengths. This
allows to explain the present dark matter density in the
universe by the freeze-out a particle, which in the early
universe was in thermal equilibrium with the rest of the
primordial plasma. This so-called “WIMP miracle” combined with the fact that models like supersymmetry predict a suitable candidate for WIMPs are the two main
reasons for its popularity. While we will try to provide
a mostly model-independent approach to dark matter,
we will nevertheless focus on the WIMP scenario and
therefore from now on use these two expressions synonymously.
∗
†
‡
§
[email protected]
[email protected]
[email protected]
[email protected]
There is a considerable experimental effort to detect
dark matter in particle physics processes. This includes
direct and indirect detection, as well as searches at particle accelerators. Direct detection relies on measuring the
nuclear recoil from a WIMP scattering off a nucleus in
a very low-background environment, consisting of either
liquid Xenon (XENON [8, 9], LUX [10]) or some solid target material (CDMS [11], EDELWEISS [12], CRESST
[13]). Indirect searches aim to find various products
of dark matter annihilation, such as γ-rays, neutrinos
or antiparticles, from sources inside and outside our
galaxy. This includes satellite-based experiments (FermiLAT [14, 15], PAMELA [16], AMS [17, 18]), groundbased experiments (H.E.S.S. [19], VERITAS [20]), and
subsurface neutrino telescopes (Super-Kamiokande [21],
ANTARES [22], IceCube [23]). Finally, searches with
the experiments ATLAS and CMS at the Large Hadron
Collider (LHC) aim to produce dark matter in collisions
of SM particles and then infer its presence from missing
energy in the final state [24, 25]. While many indirect
searches target annihilation products of WIMPs in galactic halos (e.g. the Milky Way halo) or the Galactic Center, neutrino telescopes are also sensitive to annihilation
in the center of massive celestial bodies, in particular the
Sun. In 2013 the IceCube Collaboration has published
the currently most stringent exclusion limits for WIMP
annihilations in the Sun [26]. In this paper we will interpret these results in an effective field theory approach
and compare these with searches at the LHC.
The paper is structured as follows. In Section II we
review the physics of WIMP capture and annihilation in
the Sun. The search for dark matter annihilation in the
Sun with IceCube is presented in Section III. We shall
focus on the interpretation of the search in an effective
theory with spin-dependent interactions between WIMPs
and quarks, as discussed in Section IV. Simple models of
physics beyond the SM which would lead to such effective
arXiv:1411.5817v1 [astro-ph.HE] 21 Nov 2014
Stable solitary waves in Super dense plasmas at external
magnetic fields
Azam Ghaani∗ , Kurosh Javidan†and Mohsen Sarbishaei
‡
Department of Physics, Ferdowsi University of Mashhad,
91775-1436 Mashhad, Iran
Abstract
propagation of localized waves in a Fermi-Dirac distributed super dense matter
at the presence of strong external magnetic fields is studied using the reductive perturbation method. Previous works indicate that localized waves break down in unmagnetized super dense hadronic matter. We have shown that stable solitons can be
created in such non-relativistic fluids in the presence of an external magnetic field.
Such solitary waves are governed by the Zakharov-Kuznetsov (ZK) equation. Properties of solitonic solutions are studied in media with different values of back ground
mass density and strength of magnetic field.
I. Introduction
compact astrophysical objects in the context of supernova, white dwarfs, neutron stars, etc
are results of a gravitational collapse in stars whose core mass exceed the Chandrasekhar
limit. They are the densest observable bodies in our universe and have proven to be ideal
test bodies for understanding the behaviour of matter under extreme conditions of high
pressures, densities and strong electromagnetic and gravitational fields. During the last
decade a great progress is occurred in the observational astrophysics in the direction of
studying the properties of such compact objects and specially neutron stars [1, 2, 3].
Recent observations related to anomalous x-ray pulsars and soft gamma-ray repeaters
[4, 5, 6] also prove the existence of neutron stars with very strong magnetic fields which
are known as magnetars [7, 8, 9]. The magnetic field at the surface of the magnetars
may be as strong as 1011−12 T . It is estimated that the strength of interior magnetic field
in neutron stars may be as large as 1015−16 T [10, 11]. A magnetic field of such intensity
corresponds to a force of |e|B ≈ 1GeV 2 . It is clear that this interaction can significantly
affect the properties of the system. Discoveries of huge magnetic field in neutron stars
seem to enforce us to study the effects of the magnetic field in compact stars.
Behaviour of hadronic matters in the presence of external magnetic field can be described using a set of equations which called equations of state (EOS). It may be noted
that hadronic matters with different constituents, densities and temperatures are described
with different EOS. As the density, temperature and ingredients of sections of compact
∗
Email: [email protected]
Email: [email protected]
‡
Email: [email protected]
†
1
arXiv:1411.5807v1 [nucl-th] 21 Nov 2014
Low Energy Nuclear Structure from Ultrarelativistic
Heavy-Light Ion collisions ∗
Enrique Ruiz Arriola1 and Wojciech Broniowski2,3
1
Departamento de F´ısica At´
omica, Molecular y Nuclear and Instituto Carlos I de F´ısica
Te´
orica y Computacional, Universidad de Granada, E-18071 Granada, Spain
2
Institute of Physics, Jan Kochanowski University, 25-406 Kielce, Poland
3
The H. Niewodnicza´
nski Institute of Nuclear Physics PAN, 31-342 Cracow, Poland
E-mail: [email protected] (ERA)
E-mail: [email protected] (WB)
Abstract. The search for specific signals in ultrarelativistic heavy-light ion collisions
addressing intrinsic geometric features of nuclei may open a new window to low energy nuclear
structure. We discuss specifically the phenomenon of α-clustering in 12 C when colliding with
208
Pb at almost the speed of light.
1. Introduction
Even before the neutron was discovered, based on the α decay explained successfully as a
quantum tunneling effect across the Coulomb barrier, Gamow proposed that alpha particles
(4 He nuclei) are the constituents of atomic nuclei [1]. Indeed, alpha clusters are present in light
nuclei (such as, e.g., 12 C) as effective degrees of freedom and lead to large intrinsic deformation
of their nuclear distributions, which in some cases lead to polyhedral symmetric structures:
an equilateral triangle for 12 C, tetrahedron for 16 O, trigonal bipyramid for 20 Ne, octahedron
pentagonal bipyramid for 24 Mg, hexagonal bipyramid for 28 Si, etc. [2, 3, 4, 5, 6], (for reviews
see, e.g., [7, 8, 9, 10, 11]).
A triangle hitting the wall: 12 C
pictured as a triangle of three α particles (left)
colliding with a heavy ion drawn as a round flat
object (middle). The triangular shape of the
fireball yields a triangular pattern of particle
emission after the collision (right).
Figure 1.
∗Talk by ERA at 37th Brazilian Workshop on Nuclear Physics, 8-12 September 2014, Maresias, SP, Brazil
The Cosmic Equation of State
arXiv:1411.5771v1 [astro-ph.CO] 21 Nov 2014
F. Melia1
Abstract The cosmic spacetime is often described in
terms of the Friedmann-Robertson-Walker (FRW) metric, though the adoption of this elegant and convenient
solution to Einstein’s equations does not tell us much
about the equation of state, p = wρ, in terms of the total energy density ρ and pressure p of the cosmic fluid.
ΛCDM and the Rh = ct Universe are both FRW cosmologies that partition ρ into (at least) three components, matter ρm , radiation ρr , and a poorly understood
dark energy ρde , though the latter goes one step further
by also invoking the constraint w = −1/3. This condition is apparently required by the simultaneous application of the Cosmological principle and Weyl’s postulate. Model selection tools in one-on-one comparisons
between these two cosmologies favor Rh = ct, indicating that its likelihood of being correct is ∼ 90% versus
only ∼ 10% for ΛCDM. Nonetheless, the predictions of
ΛCDM often come quite close to those of Rh = ct, suggesting that its parameters are optimized to mimic the
w = −1/3 equation-of-state. In this paper, we explore
this hypothesis quantitatively and demonstrate that the
equation of state in Rh = ct helps us to understand why
the optimized fraction Ωm ≡ ρm /ρ in ΛCDM must be
∼ 0.27, an otherwise seemingly random variable. We
show that when one forces ΛCDM to satisfy the equation of state w = (ρr /3 − ρde )/ρ, the value of the Hubble radius today, c/H0 , can equal its measured value
ct0 only with Ωm ∼ 0.27 when the equation-of-state for
dark energy is wde = −1. (We also show, however, that
the inferred values of Ωm and wde change in a correlated
fashion if dark energy is not a cosmological constant, so
that wde 6= −1.) This peculiar value of Ωm therefore
F. Melia
Department of Physics, the Applied Math Program, and Department of Astronomy, The University of Arizona, Tucson, AZ 85721
E-mail: [email protected]
1 John
Woodruff Simpson Fellow.
appears to be a direct consequence of trying to fit the
data with the equation of state w = (ρr /3 − ρde )/ρ in a
Universe whose principal constraint is instead Rh = ct
or, equivalently, w = −1/3.
Keywords cosmic microwave background; cosmological parameters; cosmology: observations; cosmology:
redshift; cosmology: theory; cosmology: dark matter;
gravitation
1 Introduction
The Cosmological principle and Weyl’s postulate appear to be essential ingredients in any physically realistic cosmological theory. Together, they posit that
the Universe is homogeneous and isotropic (at least on
large, i.e., > 100 Mpc, spatial scales), and that this
high degree of symmetry is maintained from one time
slice to the next. The appropriate spacetime to use
is conveniently and elegantly written in terms of the
Friedmann-Robertson-Walker (FRW) metric though
this, in and of itself, does not tell us much about the
cosmic equation of state, relating the total energy density ρ to its total pressure p.
In principle, if we knew these quantities precisely,
we could then solve the dynamical equations governing
the Universal expansion and understand its large-scale
structure and how it evolved to its current state. One
could then also unambiguously interpret many of the
observations, including the redshift-dependent luminosity distance to Type Ia SNe and the spectrum of fluctuations in the cosmic microwave background (CMB).
Unfortunately, we must rely on measurements and intuition to pick ρ and p. The best we can do today is to
assume that ρ must contain matter ρm and radiation ρr ,
which we see directly, and an as yet poorly understand
‘dark’ energy ρde , whose presence is required by a broad
Mon. Not. R. Astron. Soc. 000, 000–000 (0000)
Printed 24 November 2014
(MN LATEX style file v2.2)
arXiv:1411.5678v1 [astro-ph.CO] 20 Nov 2014
Cosmological Tests using the Angular Size of Galaxy Clusters
Jun-Jie Wei1,2⋆ , Xue-Feng Wu1,3,4†, and Fulvio Melia1,5 ‡
1 Purple
Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China
2 University
3 Chinese
4 Joint
of Chinese Academy of Sciences, Beijing 100049, China
Center for Antarctic Astronomy, Nanjing 210008, China
Center for Particle, Nuclear Physics and Cosmology, Nanjing University-Purple Mountain Observatory, Nanjing 210008, China
5 Department
of Physics, The Applied Math Program, and Department of Astronomy, The University of Arizona, AZ 85721, USA
24 November 2014
ABSTRACT
We use measurements of the galaxy-cluster angular size versus redshift to test and
compare the standard model (ΛCDM) and the Rh = ct Universe. We show that the
latter fits the data with a reduced χ2dof = 0.786 for a Hubble constant H0 = 72.6+3.8
−3.4
km s−1 Mpc−1 , and H0 is the sole parameter in this model. By comparison, the
optimal flat ΛCDM model, with two free parameters (including Ωm = 0.50 and
−1
H0 = 73.9+10.6
Mpc−1 ), fits the angular-size data with a reduced χ2dof =
−9.5 km s
0.806. On the basis of their χ2dof values alone, both models appear to account for the
data very well in spite of the fact that the Rh = ct Universe expands at a constant rate,
while ΛCDM does not. However, because of the different number of free parameters
in these models, selection tools, such as the Bayes Information Criterion, favour
Rh = ct over ΛCDM with a likelihood of ∼ 86% versus ∼ 14%. These results
impact the question of galaxy growth at large redshifts. Previous work suggested
an inconsistency with the underlying cosmological model unless elliptical and disk
galaxies grew in size by a surprisingly large factor ∼ 6 from z ∼ 3 to 0. The fact that
both ΛCDM and Rh = ct fit the cluster-size measurements quite well casts some
doubt on the suggestion that the unexpected result with individual galaxies may be
due to the use of an incorrect expansion scenario, rather than astrophysical causes,
such as mergers and/or selection effects.
Key words: Cosmology: theory, observations, large-scale structure—galaxies: clusters: general—galaxies:evolution
November 24, 2014
1:24
WSPC/INSTRUCTION FILE
tetra
arXiv:1411.5997v1 [hep-ph] 21 Nov 2014
International Journal of Modern Physics A
c World Scientific Publishing Company
Four-Quark Hadrons: an Updated Review
ANGELO ESPOSITO
Department of Physics, 538W 120th Street
Columbia University, New York, NY, 10027, USA
[email protected]
ANDREA L. GUERRIERI
Dipartimento di Fisica and INFN, Universit`
a di Roma ‘Tor Vergata’
Via della Ricerca Scientifica 1, I-00133 Roma, Italy
[email protected]
FULVIO PICCININI
INFN Pavia, Via A. Bassi 6, I-27100 Pavia, Italy
[email protected]
ALESSANDRO PILLONI and ANTONIO D. POLOSA
Dipartimento di Fisica and INFN, ‘Sapienza’ Universit`
a di Roma
P.le Aldo Moro 5, I-00185 Roma, Italy
[email protected], [email protected]
Received Day Month Year
Revised Day Month Year
The past decade witnessed a remarkable proliferation of exotic charmonium-like resonances discovered at accelerators. In particular, the recently observed charged states
are clearly not interpretable as q q¯ mesons. Notwithstanding the considerable advances
on the experimental side, conflicting theoretical descriptions do not seem to provide a
definitive picture about the nature of the so called XY Z particles. We present here a
comprehensive review about this intriguing topic, discussing both those experimental
and theoretical aspects which we consider relevant to make further progress in the field.
At this state of progress, XY Z phenomenology speaks in favour of the existence of compact four-quark particles (tetraquarks) and we believe that realizing this instructs us in
the quest for a firm theoretical framework.
Keywords: Exotic charmonium-like mesons; Tetraquarks; Large-N QCD; Monte Carlo
generators.
PACS numbers: 14.40.Pq, 14.40.Rt.
1
Correlation function intercepts for µ
˜, q-deformed Bose gas model implying effective
accounting for interaction and compositeness of particles
A. M. Gavrilik and Yu. A. Mishchenko
arXiv:1411.5955v1 [hep-ph] 21 Nov 2014
Bogolyubov Institute for Theoretical Physics, NAS of Ukraine, 14b, Metrolohichna Str., Kyiv 03680, Ukraine∗
In the recently proposed two-parameter µ
˜, q-deformed Bose gas model [Ukr. J. Phys. 58, 1171
(2013), arXiv:1312.1573] aimed to take effectively into account both compositeness of particles and
their interaction, the µ
˜, q-deformed virial expansion of the equation of state (EOS) was obtained.
In this paper we further explore the µ
˜ , q-deformation, namely the version of µ
˜, q-Bose gas model
involving deformed distributions and correlation functions. In the model, we explicitly derive the
one- and two-particle deformed distribution functions and the intercept of two-particle momentum
correlation function. The results are illustrated by plots, and the comparison with known experimental data on two-pion correlation function intercepts extracted in RHIC/STAR experiments is
given.
PACS numbers: 05.30.Jp, 05.90.+m, 11.10.Lm, 25.75.Gz
Keywords: Deformed Bose gas model, deformed bosons, deformation structure function, two-particle distribution and correlation function intercept, two-pion correlations at RHIC/STAR.
I.
INTRODUCTION
Deformed Bose gas models based on a set of identical
deformed (nonlinear) oscillators, or on deformed thermodynamic relations provide nonlinear extension of standard Bose gas model which finds applications to physical
systems with one or more factors of non-ideality [1–5].
In general, the effective description or modeling of essentially nonideal (nonlinear) systems usually is performed
by means of reexpressing of the physical quantities of
the initial complicated system in terms of the analogous
quantities of deformed model. Such two factors as composite structure of particles of a gas and the interaction
between them are of main interest for us here. Concerning the compositeness of particles, let us mention
the works [1, 6–8] where q-deformed oscillators were applied for effective description of composite particles (like
nuclei, nucleons, mesons, excitons, cooperons, atoms,
molecules). Their Bose-Einstein condensation was also
studied [9]. It was shown in [10, 11] that two-fermionic
(and two-bosonic) composite bosons can be algebraically
realized on their Fock states by deformed oscillator algebra with the quadratically nonlinear deformation strucˆ ) = (1 + µ
ˆ −µ
ˆ 2 , with N
ˆ
ture function (DSF) ϕµ˜ (N
˜)N
˜N
the number operator, and discrete deformation parameter µ
˜ = 1/m involved. On the other hand, q-deformation
of Arik-Coon type [12] based on the DSF equal to the
N
−1
was used for the effective de“q-bracket” [N ]q = qq−1
scription [13] of thermodynamics aspects (e.g., virial expansion) of Bose gas with interaction. So far, two aspects
were treated separately, adhering to different methods
and contexts. However, the task naturally arises of treating jointly: i) compositeness of particles linked, through
the realization, with quadratic or µ
˜-deformation; ii) the
interaction between particles modeled by q-deformation.
∗
[email protected]
We may expect that combining these two types of deformation into single one will reproduce effectively, in
a unified manner, some specific features inherent to the
thermodynamic or statistical quantities of more realistic systems of particles possessing both interaction and
compositeness. The simplest variant of such unification
is their functional composition or µ
˜, q-deformation. Of
course, at the moment the ascription of the meaning of
deformation parameters µ
˜ and q as responsible respectively for the compositeness and the interaction is rather
formal, and the detailed consistent analysis providing a
reformulation in the deformed model terms, including the
relation with the parameters of interaction or compositeness, is not completed to sufficient extent.
First steps to the (microscopics of) effective taking
of interaction and compositeness jointly into account
are made by introducing the µ
˜ , q-deformed Bose gas
model [3, 4] based on deforming the thermodynamics.
Namely, in [3] the µ
˜ , q-deformed Bose gas model was realized through deforming the total mean number of particles or the partition function by means of the deformed
d
analog of the derivative z dz
(z is fugacity) and use of the
“hybrid” (combined) DSF
d
h di
ϕµ˜ ,q z
≡ ϕµ˜ (Dq ) = (1+ µ
˜)Dq − µ
˜Dq2 , Dq ≡ z
. (1)
dz
dz q
This version of µ
˜, q-Bose gas model was constructed bearing in mind the goal of effective description of thermodynamics of interacting gas of composite bosons (made of
two bosons or two fermions). In fact, the latter due to
compositeness are no longer true bosons. For that model,
the deformed virial expansion was studied. In the sequel
to [3], the relation of the obtained virial coefficients of
the (˜
µ, q)-deformed model (dependent explicitly on the
deformation parameters µ
˜ and q) with scattering data
of some interaction was explored [4], and the arising unusual temperature dependence of µ
˜ and q discussed and
justified.
The version of µ
˜ , q-deformed Bose gas model consid-
Searching for Traces of Planck-Scale Physics with High Energy Neutrinos
Floyd W. Stecker
Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA and
Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095
Sean T. Scully
Department of Physics and Astronomy,
James Madison University
Harrisonburg, VA 22807, USA
arXiv:1411.5889v1 [hep-ph] 21 Nov 2014
Stefano Liberati
SISSA - International School for Advanced Studies
Via Bonomea 265, Trieste 34136, Italy and
INFN Sezione di Trieste, Trieste, Italy
David Mattingly
Department of Physics, University of New Hampshire
Durham, New Hampshire 03824, USA
High energy cosmic neutrino observations provide a sensitive test of Lorentz invariance violation
(LIV), which may be a consequence of quantum gravity theories. We consider a class of nonrenormalizable, Lorentz invariance violating operators that arise in an effective field theory (EFT)
description of Lorentz invariance violation in the neutrino sector inspired by Planck-scale physics
and quantum gravity models. We assume a conservative generic scenario for the redshift distribution of extragalactic neutrino sources and employ Monte Carlo techniques to describe superluminal
neutrino propagation, treating kinematically allowed energy losses of superluminal neutrinos caused
by both vacuum pair emission (VPE) and neutrino splitting. We consider EFTs with both nonrenormalizable CPT -odd and non-renormalizable CPT -even operator dominance. We then compare
the spectra derived using our Monte Carlo calculations in both cases with the spectrum observed
by IceCube in order to determine the implications of our results regarding Planck-scale physics. We
find that if the drop off in the neutrino flux above ∼ 2 PeV is caused by Planck scale physics, rather
than by a limiting energy in the source emission, a potentially significant pileup effect would be
produced just below the drop off energy in the case of CPT -even operator dominance. However,
such a clear drop off effect would not be observed if the CPT -odd, CPT -violating term dominates.
PACS numbers:
I.
INTRODUCTION
General relativity has been a fundamental tenet of
physics for almost a century. Similarly, quantum field
theory has also proved crucial to a deep understanding
of physics, both as a fundamental framework to describe
subatomic particles, and as a framework that describes
emergent phenomena in condensed matter. However,
merging the two theories naively yields
p an incomplete
theory at the Planck scale of λP l = G¯
h/c3 ∼ 10−35
m [1] as general relativity is not perturbatively renormalizable. In their efforts to provide a UV (i.e., high
energy) completion for quantum general relativity, many
quantum gravity theories introduce drastic modifications
to space-time at the Planck scale (e.g., [2]). Examples of
this are extra dimensions theories and postulating fundamental discreteness of space-time, with the building
blocks of nature being extended objects.
One possible modification to space-time structure that
has received quite a bit of attention is the idea that
Lorentz symmetry is not an exact symmetry of nature.
Such a proposal is rather tame when compared with
other quantum gravity ideas as historically the symmetry groups used to model physical phenomena have inevitably evolved over time. Lorentz symmetry violation
has been explored within string theory [3], loop quantum gravity, Hoˇrava-Lifshitz gravity, causal dynamical
triangulations, non-commutative geometry, doubly special relativity, among others (see, e.g., Refs. [4] and [5]
and references therein). While it is not possible to directly investigate space-time physics at the Planck energy of ∼ 1019 GeV, many lower energy testable effects
have been predicted to arise from the violation of Lorentz
invariance (LIV) at or near the Planck scale. The subject
of investigating LIV has therefore generated much interest in the particle physics and astrophysics communities.
In this paper we propose using high energy astrophysical neutrino data to search for traces of such Planck-scale
physics. We use the IceCube data [6] to investigate the
possible effects of LIV terms arising within the context of
an effective field theory (EFT) such as generalized in the
standard model extension (SME) formalism. We concentrate on the lowest order Planck-mass suppressed operators, viz., the mass dimension [d] = 5 and [d] = 6 terms
KEK-TH-1780
Quark mixing from ∆(6N 2) family symmetry
arXiv:1411.5845v1 [hep-ph] 21 Nov 2014
Hajime Ishimori,1 Stephen F. King,2 Hiroshi Okada,3 Morimitsu Tanimoto4
1
Institute of Particle and Nuclear Studies,
High Energy Accelerator Research Organization (KEK)
Tsukuba 305-0801, Japan
2
School of Physics and Astronomy, University of Southampton,
Southampton, SO17 1BJ, U.K.
3
4
School of Physics, KIAS, Seoul 130-722, Korea
Department of Physics, Niigata University, Niigata 950-2181, Japan
Abstract
We consider a direct approach to quark mixing based on the discrete family symmetry
∆(6N 2 ) in which the Cabibbo angle is determined by a residual Z2 ×Z2 subgroup to be
|Vus | = 0.222521, for N being a multiple of 7. We propose a particular model in which
unequal smaller quark mixing angles and CP phases may occur without breaking the
residual Z2 × Z2 symmetry. We perform a numerical analysis of the model for N = 14,
where small Z2 × Z2 breaking effects of order 3% are allowed by model, allowing
perfect agreement within the uncertainties of the experimentally determined best fit
quark mixing values.
Right-handed lepton mixings at the LHC
Juan Carlos Vasquez1, 2
2
1
SISSA/INFN, via Bonomea, 265 - 34136 Trieste, Italy
Gran Sasso Science Institute, Viale Crispi 7, 67100 LAquila, Italy.
(Dated: November 24, 2014)
arXiv:1411.5824v1 [hep-ph] 21 Nov 2014
We study how the elements of the leptonic right-handed mixing matrix can be determined at the
LHC in the minimal Left-Right symmetric extension of the standard model. We do it by explicitly
relating them with physical quantities of the Keung-Senjanovi´c process and the lepton number
violating decays of the right doubly charged scalar. We also point out that the left and right doubly
charged scalars can be distinguished at the LHC, without measuring the polarization of the final
state leptons coming from their decays.
I.
INTRODUCTION
The Left-Right symmetric theory is based on the gauge
group SU (2)L × SU (2)R × U (1)B−L [1, 2], times a LeftRight symmetry that may be generalized parity (P) or
charge conjugation (C) (for reviews see [3]). It introduces three new heavy gauge bosons WR+ , WR− , ZR and
the heavy neutrino states N . In this model, the maximally observed parity non conservation is a low energy
phenomenon, which ought to disappear at energies above
the WR mass. Furthermore, the smallness of neutrino
masses is related to the near maximality of parity violation [4–6], through the seesaw mechanism [4–7].
Theoretical bounds on the Left-Right scale were considered in the past. The small KL − KR mass difference
gives a lower bound on the Left-Right-scale of around 3
TeV in the minimal model [8]. More recently in [9], an
updated study and a complete gauge invariant computation of the KL , KS and Bd , Bs meson parameters, gives
MWR > 3.1(2.9) TeV for P(C). In [10] it is claimed that
for parity as the Left-Right symmetry, the θQCD parameter, together with K-meson mass difference ∆MK , push
the mass of WR up to 20 TeV [9, 10]; however this depends on the UV completion of the theory [11]. Direct
LHC searches, on the other hand, gives in some channels
a lower bound of around 3 TeV [12].
It turns out that there exists [13] an exiting decay
of WR into two charged leptons and two jets (WR →
l + N → ll + jj). We refer to it as the Keung-Senjanovi´c
(KS) process. This process has a small background and
no missing energy. It gives a clean signal for the WR production at LHC, as well as probing the Majorana masses
of the heavy neutrinos. Since there is no missing energy
in the decay, the reconstruction of the WR and N invariant masses is possible. If true, the Majorana mass of N
will lead to the decay of the heavy neutrino into a charged
lepton and two jets (N → l + jj), with the same probability of decaying into a lepton or antilepton. Recetly
CMS gives and excess in the ee-channel of 2.8σ for this
particular process at Meejj ≈ 2.1TeV [12]. In [14, 15] it
is shown that this excess can be accommodated with a
higher Left-Right symmetry breaking scale. Next LHC
run will be crucial to establish or discard this excess.
The production of WR is ensured at the LHC because
in the quark sector the left and right mixing matrices are
related. For C as the Left-Right symmetry, the mixing
angles are exactly equal, therefore the production rate of
WR is the same as the one of W . For P the situation
is more subtle and needed an in-depth study. Finally
in [16] a simple analytic expression valid in the entire
parameter space was derived for the right-handed quark
mixing matrix. It turns out that despite parity being
maximally broken in nature, the Right and Left quark
mixing matrices end up being very similar.
In the Leptonic sector the connection between the Left
and Right leptonic mixing matrices goes away, since light
and heavy neutrino masses are different. For C as the
Left-Right symmetry, the Dirac masses of neutrinos are
unambiguously determined in terms of the heavy and
light neutrino masses [17]. Light neutrino masses are
probed by low energy experiments, whereas the ones of
the heavy neutrinos can be determined at the LHC. This
is why the precise determination of the right-handed leptonic mixing matrix, the main topic of this work, is of
fundamental importance.
We focus on the determination of the elements of the
leptonic mixing matrix VR at the LHC, through the KS
++
process and the decays of the doubly-charged scalar δR
belonging to the SU (2)R triplet. We point out that these
two processes are not sensitive to three of the phases appearing in VR , unlike electric dipole moments of charged
leptons.
The rest of this paper is organized as follows. In Section 2 we give a brief description of the model and the
main relevant interactions for our purposes. In Section
3 we show the determination of the three mixing angles
and the “Dirac” type phase appearing in VR . We do it in
terms of physical observables in the KS process. We also
show for C as the Left-Right symmetry, how the branch++
ing ratios of the doubly charged scalar δR
into e+ e+ ,
+ +
+ +
e µ and µ µ can be used to determine the Majorana
type phases. We consider for illustration the type II seesaw dominance and put some representative values for
the “Dirac” phase, the lightest and the heaviest righthanded neutrino masses. Finally, in section 4 we show
++
++
that the doubly charged scalars δL
and δR
may be
distinguished at the LHC, without measuring the polarization of the charged leptons coming from their decays.
arXiv:1411.5800v1 [hep-ph] 21 Nov 2014
UNIVERSITY OF SOUTHAMPTON
Collider phenomenology of the
4D composite Higgs model
by
Daniele Barducci
A thesis submitted in partial fulfillment for the
degree of Doctor of Philosophy
in the
Faculty of Physical Sciences and Engineering
School of Physics and Astronomy
September 2014
UNIVERSITY OF SOUTHAMPTON
Abstract
Faculty of Physical Sciences and Engineering
School of Physics and Astronomy
Doctor of Philosophy
by Daniele Barducci
This Thesis is devoted to the phenomenological analysis at the large hadron collider
(LHC), as well at a future electron positron collider, of the 4 dimensional (4D) composite
Higgs model (4DCHM), a compelling beyond the standard model scenario where the
Higgs state arises as a pseudo Nambu Goldstone boson. The motivations and the main
characteristics of the model are summarised and then an analysis of the gauge and Higgs
sectors of the 4DCHM is performed. Finally we propose a general framework for the
analysis of models with an extended quark sector that we have applied to a simplified
composite Higgs scenario.
BBN And The CMB Constrain Neutrino Coupled Light WIMPs
Kenneth M. Nollett1, 2, 3, ∗ and Gary Steigman4, 5, †
1
Department of Physics and Astronomy, University of South Carolina, 712 Main St., Columbia, SC 29208, USA
2
Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA
3
Department of Physics, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-1233
4
Center for Cosmology and AstroParticle Physics, Ohio State University,
5
Department of Physics, Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210, USA
(Dated: November 24, 2014)
arXiv:1411.6005v1 [astro-ph.CO] 21 Nov 2014
In the presence of a light weakly interacting massive particle, a WIMP with mass mχ <
∼ 30 MeV,
there are degeneracies among the nature of the WIMP (fermion or boson), its couplings to the
standard model particles (to electrons, positrons, and photons, or only to neutrinos), its mass mχ ,
and the number of equivalent (additional) neutrinos, ∆Nν . These degeneracies cannot be broken
by the cosmic microwave background (CMB) constraint on the effective number of neutrinos, Neff .
However, since big bang nucleosynthesis (BBN) is also affected by the presence of a light WIMP and
equivalent neutrinos, complementary BBN and CMB constraints can help to break some of these
degeneracies. In a previous paper [1] the combined BBN and Planck [2] CMB constraints were used
to explore the allowed ranges for mχ , ∆Nν , and Neff in the case where the light WIMPs annihilate
electromagnetically (EM) to photons and/or e± pairs. In this paper the BBN predictions for the
primordial abundances of deuterium and 4 He (along with 3 He and 7 Li) in the presence of a light
WIMP that only couples (annihilates) to neutrinos (either standard model – SM – only or both
SM and equivalent) are calculated. Recent observational estimates of the relic abundances of D
and 4 He are used to limit the light WIMP mass, the number of equivalent neutrinos, the effective
number of neutrinos, and the present Universe baryon density (ΩB h2 ). Allowing for a neutrino
coupled light WIMP and ∆Nν equivalent neutrinos, the combined BBN and CMB data provide
lower limits to the WIMP mass that depend very little on the nature of the WIMP (Majorana or
Dirac fermion, real or complex scalar boson), with a best fit mχ >
∼ 35 MeV, equivalent to no light
WIMP at all. In the absence of a light WIMP (either EM or neutrino coupled), BBN alone prefers
∆Nν = 0.50±0.23, favoring neither the absence of equivalent neutrinos (∆Nν = 0), nor the presence
of a fully thermalized sterile neutrino (∆Nν = 1). This result is consistent with the CMB constraint,
Neff = 3.30 ± 0.27 [2], constraining “new physics” between BBN and recombination. Combining the
BBN and CMB constraints gives ∆Nν = 0.35 ± 0.16 and Neff = 3.40 ± 0.16. As a result, while BBN
and the CMB combined require ∆Nν ≥ 0 at ∼ 98 % confidence, they disfavor ∆Nν ≥ 1 at > 99 %
confidence. Adding the possibility of a neutrino-coupled light WIMP extends the allowed range
slightly downward for ∆Nν and slightly upward for Neff simultaneously, while leaving the best-fit
values unchanged.
∗
†
[email protected]
[email protected]
arXiv:1411.5753v1 [nucl-th] 21 Nov 2014
Study of isospin nonconservation in the framework of
spectral distribution theory
Kamales Kar⋆,a and Sukhendusekhar Sarkar†,b
⋆
†
Ramakrishna Mission Vivekananda University,Belur Math, Howarah 711202, India
Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India
ABSTRACT
The observed isospin-symmetry breaking in light nuclei are caused not only by the Coulomb
interaction but by the isovector one and two body plus isotensor two body nuclear interactions as
well. Spectral distribution theory which treats nuclear spectroscopy and other structural properties
in a statistical framework was earlier applied to isospin conserving Hamiltonians only. In this paper
we extend that to include the nuclear interactions non-scalar in isospin and work out examples in
sd shell to calculate the linear term in the isobaric mass-multiplet equation originating from these
non-scalar parts.
a
b
email: [email protected]
email: [email protected] ; [email protected]
Jet transport and photon bremsstrahlung via longitudinal and transverse scattering
Guang-You Qin1, 2 and Abhijit Majumder2
arXiv:1411.5642v1 [nucl-th] 20 Nov 2014
1
Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE),
Central China Normal University, Wuhan, 430079, China
2
Department of Physics and Astronomy, Wayne State University, Detroit, MI, 48201.
(Dated: November 21, 2014)
We study the effect of multiple scatterings on the propagation of hard partons and the production
of jet-bremsstrahlung photons inside a dense medium in the framework of deep-inelastic scattering
off a large nucleus. We include the momentum exchanges in both longitudinal and transverse
directions between the hard partons and the constituents of the medium. Keeping up to the second
order in a momentum gradient expansion, we derive the spectrum for the photon emission from
a hard quark jet when traversing dense nuclear matter. Our calculation demonstrates that the
photon bremsstrahlung process is influenced not only by the transverse momentum diffusion of the
propagating hard parton, but also by the longitudinal drag and diffusion of the parton momentum.
A notable outcome is that the longitudinal drag tends to reduce the amount of stimulated emission
from the hard parton.
I.
INTRODUCTION
The modification of hard partonic jets in dense media provides a useful tool for studying the properties of
the highly excited nuclear matter produced in relativistic heavy-ion collisions. One of the primary experimental
signatures for jet modification is the significant depletion
of the high transverse momentum (pT ) hadron yield in
heavy-ion collisions compared to that in binary-scaled
proton-proton collisions [1–3]. Such depletion has been
attributed to the loss of the forward momentum and energy by the hard partons in the dense nuclear medium
they traversed before fragmenting into hadrons [4, 5].
By all account, one expects the energy loss to originate from a combination of elastic collisions [6–10] and
inelastic radiative processes [4, 5, 11–13] that hard jets
experience when propagating through the dense media.
For the light partons, the medium-induced gluon radiation is thought to be the more dominant mechanism for
the parton energy loss. For heavy flavor partons with
large finite masses, collisional energy loss appears to be
equally or even more important than medium-induced
gluon radiation, especially at low and intermediate pT
regime [14–18].
There are currently a few different schemes for the
study of medium-induced gluon bremsstrahlung and
radiative part of parton energy loss in dense nuclear medium, namely, Baier-Dokshitzer-Mueller-PeigneSchiff-Zakharov (BDMPS-Z) [11–13], Gyulassy, Levai
and Vitev (GLV) [19–21], Amesto-Salgado-Wiedemann
(ASW) [22, 23], Arnold-Moore-Yaffe (AMY) [24, 25] and
higher twist (HT) [26–28] formalisms. More detailed
comparison of different formalisms may be found in Ref.
[29]. Sophisticated phenomenological have been performed for various jet quenching observables, such as
single inclusive hadron suppression [30–32], as well as dihadron and photon-hadron correlations [33–36]. One of
the main goals of these studies is to quantitatively extract
the jet transport parameters, such as qˆ and eˆ, in dense
media by comparing with the data on jet modification.
This requires that the overarching formalisms contain a
representative description of all physical processes that
influence the partonic substructure of the jet.
While different parton energy loss models mentioned
above have rather different origins and make slightly different approximations, the calculations of radiative energy loss have so far only focused on the gluon radiation
induced by transverse momentum diffusion experienced
by the propagating hard partons in the dense medium. In
fact, when a jet scatters off the medium constituents, it is
not only the transverse momentum, but also the longitudinal momentum that are exchanged between the jet and
the medium [37–39]. In many calculations, the transfer of
longitudinal momentum has only been considered in the
evaluation of purely collisional energy loss. There have
been studies on the longitudinal momentum loss experienced by radiated partons in the context of jet shower
evolution [40–43]. However, the influence of exchanging longitudinal momentum on the stimulated radiation
vertex has not yet been considered. In this work, we reinvestigate the medium-induced radiation, by taking into
account the influence from both transverse and longitudinal momentum transfers when jets undergo multiple
scatterings with the medium in the radiation process.
As a step up to more complicated calculation of gluon
radiation, we study the problem of real photon radiation
from a partonic jet which propagates through a dense
medium and experiences multiple scatterings of gluons.
While the emitted photon escapes the medium without
further strong-interaction with medium, very unlike the
case of a radiated gluon, such a problem does encode
many interesting features of the medium-induced gluon
radiation, such as the Landau-Pomeranchuck-Migidal
(LPM) effect, as well as the approximation schemes involved in the problem, which are the same as the problem
with gluon radiation. Therefore, the photon calculation
serves as an intermediate step for the further investigation of medium-induced gluon emission from a hard jet.
In addition, photon bremsstrahlung from a high pT
jet is itself of great interest. Such process has shown
Pion-pion cross section from proton-proton collisions at the LHC
B. Z. Kopeliovich, I. K. Potashnikova, and Iv´an Schmidt
1
Departamento de F´ısica, Universidad T´ecnica Federico Santa Mar´ıa; and
Centro Cient´ıfico-Tecnol´
ogico de Valpara´ıso; Casilla 110-V, Valpara´ıso, Chile
H. J. Pirner1 and K. Reygers2
arXiv:1411.5602v1 [hep-ph] 20 Nov 2014
1
Institute for Theoretical Physics, University of Heidelberg, Germany
2
Physikalisches Institut, University of Heidelberg, Germany
The pion-pion total cross section at high energies, unknown from data, can be extracted from
proton-proton collisions with production of forward-backward leading neutrons, pp → n X n. The
zero-degree calorimeters (ZDC) installed in the ALICE, ATLAS, and CMS experiments at the LHC,
make such a measurement possible. One can also access elastic ππ scattering measuring the exclusive
two-pion production channel, pp → n π + π + n. An analysis aimed at extraction of the pion-pion
cross section from data is strongly affected by absorptive corrections, which can also be treated as
a survival of rapidity gaps. The study of absorption effects is the main focus of the present paper.
These effects are studied on the amplitude level and found to be different between the pion flux,
which conserves the nucleon helicity, and the one which flips helicity. Both fluxes are essentially
reduced by absorption, moreover, there is a common absorption suppression factor, which breaks
down the factorized form of the cross section. We also evaluated the contribution of other iso-vector
Reggeons, ρ, a2 and a1 .
PACS numbers: 13.85.Dz, 13.85.Lg, 13.85.Ni, 14.20.Dh
I.
INTRODUCTION
The proton-proton elastic scattering cross section has
been measured in a wide range of energies,
and recently
√
up to the highest energy of the LHC, s = 7 TeV [1, 2].
At the same time, measurements of the pion-nucleon
cross section have been
√ restricted so far to rather low
energies, up to about s = 35 GeV [3]. The pion-pion
cross section cannot be measured directly, and has been
extracted from data only at very low energies near threshold [4]. The theoretical description of elastic scattering
has been based so far only on phenomenological models.
Even the simplest versions of Regge models, assuming
Pomeron pole dominance (no cuts) [5] still describe the
available data reasonably well, in spite of the obvious
problems with the unitarity bound at higher energies.
Among the unitarized models [6–11], a precise prediction of the elastic cross section at the LHC was done in
[12, 13]. In contrast to the models treating teh Pomeron
as a simple Regge pole, an increasing rate of the energy
dependence was predicted. Even a steeper rise of the
cross sections at high energies is expected for π-p and
π-π scattering. The models [14] based on non perturbative interaction dynamics fixed at low energies, predict
an increasing cross section with energy. These models
provided predictions for pp, πp and ππ cross sections.
The possibility of having a pion-pion collider does not
seem to be realistic, and it has not been seriously considered so far. However, one can make use of virtual
pion beams. Indeed, nucleons are known to have pion
clouds, with low virtuality, so high energy proton beams
are accompanied by an intensive flux of high-energy pions, which participate in collisions. This way to measure
electron-pion collisions was employed in the ZEUS [15]
and H1 [16] experiments at HERA. Pion contribution
was singled out by detecting leading neutrons with large
fractional momentum, z. The main objective of these
measurements was the determination of the pion structure function F2π (x, Q2 ) at low x. This task turned out
to be not straightforward, because of absorptive corrections, which suppress the cross section. In fact, recent
study of these effects [24] found them to be quite strong,
reducing significantly the cross section. A good description of data was achieved. A weaker effect of absorption
was expected in Refs. [17–20].
Detecting leading neutrons with large z in pp collisions one can access the π-p total cross section at energies much higher than with real pion beams. Apparently,
the absorptive corrections in this case should be similar
or stronger than in γ ∗ -p collisions. A detailed study of
these effects was performed in [25]. However, no data
from modern colliders have been available so far, except
for a few points with large error bars from the PHENIX
experiment [21, 22] and old data from ISR [23]. The
normalization of the latter was found unreliable in [25].
Earlier attempts to extract the ππ and πp cross sections from neutron production at low energies of fixed
target experiments were made in [26, 27], although no
absorptive corrections were introduced.
The experiments ATLAS, CMS and ALICE at the
LHC, are equipped with zero-degree calorimeters, which
are able to detect neutrons at very small angles. This
is ideal for experimenting with pions accompanying the
colliding protons. In particular, detecting leading neutrons, simultaneously produced in both directions, one
can accesses pion-pion collisions at high c.m. energy,
sππ = (1 − z1 )(1 − z2 )s, where z1,2 are the fractional momenta of the detected neutrons. Naturally, this process is
Quarkonia Disintegration due to time dependence of the q q¯ potential in Relativistic
Heavy Ion Collisions
Partha Bagchi∗ and Ajit M. Srivastava†
Institute of Physics, Bhubaneswar, Odisha, India 751005
arXiv:1411.5596v1 [hep-ph] 20 Nov 2014
Rapid thermalization in ultra-relativistic heavy-ion collisions leads to fast changing potential
between a heavy quark and antiquark from zero temperature potential to the finite temperature
one. Time dependent perturbation theory can then be used to calculate the survival probability
of the initial quarkonium state. In view of very short time scales of thermalization at RHIC and
LHC energies, we calculate the survival probability of J/ψ and Υ using sudden approximation. Our
results show that quarkonium decay may be significant even when temperature of QGP remains low
enough so that the conventional quarkonium melting due to Debye screening is ineffective.
PACS numbers: PACS numbers: 25.75.-q, 11.27.+d, 14.40.Lb, 12.38.Mh
Suppression of heavy quarkonia as a signal for the
quark-gluon plasma phase in relativistic heavy-ion collisions has been investigated intensively since the original
proposal by Matsui and Satz [1]. The underlying physical
picture of this suppression is that due to deconfinment,
potential between q q¯ gets Debye screened, resulting in
the swelling of quarkonia. If the Debye screening length
of the medium is less than the radius of quarkonia, then
q q¯ may not form bound states, leading to melting of the
initial quarkonium. Due to this melting, the yield of
quarkonia will be suppressed. This was proposed as a
signature of QGP and has been observed experimentally
[2]. However, there are other factors too that can lead
to the suppression of J/ψ because of which it has not
been possible to use J/ψ suppression as a clean signal
for QGP.
In the above picture, suppression of quarkonia occurs
when the temperature of QGP achieves a certain value,
TD , so that the Debye screening melts the quarkonium
bound state. Thus, if the temperature remains smaller
than TD , so that Debye screening length remains larger
than the quarkonia size, no suppression is expected. This
type of picture is consistent with the adiabatic evolution
of a quantum state under changing potential. Original
quarkonia has a wave function appropriate for zero temperature potential between a q and q¯. If the environment
of the quarkonium changes to a finite temperature QGP
adiabatically, with Debye screened potential, the final
state will evolve to the quarkonium state corresponding to the finite temperature potential. If temperature
remains below TD , quarkonium wave function changes
(adiabatically) but it survives as the quarkonium.
We question this assumption of adiabatic evolution for
ultra-relativistic heavy-ion collisions, such as at RHIC,
and especially at LHC. At such energies, it is possible that thermalization is achieved in a very short time,
about 0.25 fm for RHIC and even smaller about 0.1 fm for
∗ Electronic
† Electronic
address: [email protected]
address: [email protected]
LHC [3]. Even conservatively, thermalization is achieved
within 1 fm as suggested by the elliptic flow measurements [4]. For J/ψ and even for Υ, typical time scale of
q q¯ dynamics will be at least 1-2 fm from the size of the
bound state and the fact that q q¯ have non-relativistic velocities. Also, ∆E between J/ψ and its next excited state
(χ) is about 300 MeV (400 MeV for Υ states), leading to
transition time scale ∼ 0.7 fm (0.5 fm for Υ). Thus the
change in the potential between q and q¯ occurs in a time
scale which is at most of the same order, and likely much
shorter than, the typical time scale of the dynamics of the
q q¯ system, or the time scale of transition between relevant states. The problem, therefore, should be treated
in terms of a time dependent perturbation and survival
probability of quarkonia should be calculated under this
perturbation. It is immediately clear that even if the final
temperature remains less than TD , if the change in potential is fast enough invalidating the adiabatic assumption, then transition of initial quarkonium state to other
excited states will occur. Such excited states will have
much larger size, typically larger than the Debye screening length, and will melt away. Thus quarkonia melting
can occur even when QGP temperature remains below
TD . We mention that adiabatic evolution of quarkonia
states has been discussed earlier for the cooling stage of
QGP in relativistic heavy ion collisions in the context of
sequential suppression of quarkonia states [5]. However,
as far as we are aware, validity of adiabatic evolution
during the thermalization stage has not been discussed
earlier.
Given the large difference between thermalization time
scale of order 0.1 - 0.2 fm [3], and the time scale of q q¯
dynamics in a quarkonium bound state being of order 1-2
fm (or the time scale of transition between relevant states
being 0.5 - 0.7 fm), it may be reasonable to use the sudden
perturbation approximation. The initial wave function of
the quarkonium cannot change under this sudden perturbation. Thus, as soon as thermalization is achieved with
QGP temperature being T0 (which may remain less than
TD for the quarkonium state under consideration), the
initial quarkonium wave function is no longer an energy
eigen state of the new Hamiltonian with the q q¯ potential
Neutron Time-Of-Flight Spectrometer Based on HIRFL for Studies of
Spallation Reactions Related to ADS Project
ZHANG Suyalatu1,2 , CHEN Zhiqiang1,*, HAN Rui 1 , WADA Roy1 , LIU Xingquan 1,2 , LIN
Weiping1,2 , LIU Jianli 1 , SHI Fudong1 , REN Peipei 1,2 , TIAN Guoyu 1,2 , LUO Fei 1
1
Institute of Modern Physics, Chinese Academy of Sciences, Gansu, Lanzhou 730000, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
*
Corresponding author. E-mail address: [email protected]
Abstract: A Neutron Time-Of-Flight (NTOF) spectrometer based on Heavy Ion Research Facility in
Lanzhou (HIRFL) is developed for studies of neutron production of proton induced spallation
reactions related to the ADS project. After the presentation of comparisons between calculated
spallation neutron production double-differential cross sections and the available experimental one, a
detailed description of NTOF spectrometer is given. Test beam results show that the spectrometer
works well and data analysis procedures are established. The comparisons of the test beam neutron
spectra with those of GEANT4 simulations are presented.
Key words: Time-Of-Flight spectrometer, Neutron production cross section, Spallation reaction,
ADS project, GEANT4
I.
Introduction
A great interest of spallation reactions
[1,2]
has been increasing with the development of
Accelerator Driven Systems (ADS) and the applications of Spallation Neutron Source (SNS). The
spallation reaction is defined as interactions between a light projectile (e.g. proton) with the GeV
range energy and heavy target nuclei which is split to a large number of hadrons (mostly neutrons)
or fragments. Many nuclear models, such as intra-nuclear cascade-evaporation (INC/E)
and quantum molecular dynamics (QMD) model
[4]
[3]
model
, have been developed to study spallation
reactions. These nuclear models are coded for thin-target simulations. In order to perform
calculations for practical applications, which may involve complex geometries and multiple
composite materials, nuclear models need to be embedded into a sophisticated transport code. The
combination of nuclear models with a Monte Carlo transportation code like MCNP [5], GEANT4 [6,7]
and FLUKA
[8,9]
, nucleon meson transport codes (NMTC)
facilities of engineering applications of the spallation reaction.
[10]
are widely utilized for designing
Characterizing flow fluctuations with moments
Rajeev S. Bhalerao,1 Jean-Yves Ollitrault,2 and Subrata Pal3
arXiv:1411.5160v1 [nucl-th] 19 Nov 2014
2
1
Department of Theoretical Physics, TIFR, Homi Bhabha Road, Colaba, Mumbai 400 005, India
CNRS, URA2306, IPhT, Institut de physique th´eorique de Saclay, F-91191 Gif-sur-Yvette, France
3
Department of Nuclear and Atomic Physics, TIFR, Homi Bhabha Road, Mumbai, 400005, India
(Dated: November 20, 2014)
We present a complete set of multiparticle correlation observables for ultrarelativistic heavy-ion
collisions. These include moments of the distribution of the anisotropic flow in a single harmonic,
and also mixed moments, which contain the information on correlations between event planes of
different harmonics. We explain how all these moments can be measured using just two symmetric
subevents separated by a rapidity gap. This presents a multi-pronged probe of the physics of flow
fluctuations. For instance, it allows to test the hypothesis that event-plane correlations are generated
by non-linear hydrodynamic response. We illustrate the method with simulations of events in A
MultiPhase Transport (AMPT) model.
PACS numbers: 25.75.Ld, 24.10.Nz
I.
INTRODUCTION
Large anisotropic flow has been observed in ultrarelativistic nucleus-nucleus collisions at the Relativistic
Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) [1]. Anisotropic flow is an azimuthal (ϕ)
asymmetry of the single-particle distribution [2]:
P (ϕ) =
+∞
1 X
Vn e−inϕ ,
2π n=−∞
(1)
where Vn is the (complex) anisotropic flow coefficient in
the nth harmonic. One usually uses the notation vn for
the magnitude: vn ≡ |Vn |. Anisotropic flow is understood as the hydrodynamic response to spatial deformation of the initial density profile. This profile fluctuates
event to event, which implies that the flow also fluctuates [3, 4]. The recognition of the importance of flow
fluctuations has led to a wealth of new flow observables,
among which triangular flow [5] and higher harmonics,
as well as correlations between different Fourier harmonics [6].
Flow fluctuations provide a window [7] into both the
early stage dynamics and the transport properties of
the quark-gluon plasma. Specifically, the magnitudes of
higher-order harmonics (V3 to V6 ) are increasingly sensitive to the shear viscosity to entropy density ratio [8].
The distributions of V2 and V3 carry detailed information about the initial density profile [9, 10], while V4 and
higher harmonics are understood as superpositions of linear and nonlinear responses, through which they are correlated with lower-order harmonics [11, 12]. Ideally, one
would like to measure the full probability distribution
p(V1 , V2 , · · · , Vn ) [13]. So far, only limited information
has been obtained, concerning either the distribution of
a single Vn [14] or specific angular correlations between
different harmonics [6].
We propose to study the distribution p(V1 , V2 , · · · , Vn )
via its moments in various harmonics [15, 16], either single or mixed, and illustrate our point with realistic sim-
ulations using the AMPT model [17]. In Sec. II, we recall how moments can be measured simply with a single rapidity gap [18]. This procedure is less demanding
in terms of detector acceptance than the one based on
several rapidity windows separated pairwise by gaps [6],
and can be used to study even four-plane correlators.
In Sec. III, we list standard measures of flow fluctuations which have been used in the literature and express
them in terms of moments. In Sec. IV, we introduce
new observables which shed additional light on the origin of event-plane correlations. For instance, a correlation between (V2 )2 and V4 has been observed, which
increases with impact parameter [6]. This correlation is
usually understood [19] as an effect of the non-linear hydrodynamic response which creates a V4 proportional to
(V2 )2 [11, 20, 21]: the increase in the correlation is thus
assumed to result from the increase of elliptic flow [22].
We show that this hypothesis can be tested directly by
studying how the correlation between (V2 )2 and V4 is
correlated with the magnitude of V2 . We also investigate
in a similar way the origin of the three-plane correlation
between V2 , V3 and V5 [6].
II.
MEASURING MOMENTS
The statistical properties of Vn are contained in its
moments, which are average values of products of Vn , of
the form
*
+
Y
∗ ln
kn
M≡
,
(2)
(Vn ) (Vn )
n
where kn and ln are integers, and angular brackets denote an average value over events. Note that Vn∗ = V−n
and V0 = 1. Azimuthal symmetry implies that the only
nontrivial moments satisfy [23]
X
X
nkn =
nln .
(3)
n
n
Charge topology of coherent dissociation of
11
C and
12
N relativistic nuclei
D. A. Artemenkov, V. Bradnova, A. A. Zaitsev, P. I. Zarubin, I. G. Zarubina, R. R. Kattabekov,
N. K. Kornegrutsa, K. Z. Mamatkulov, P. A. Rukoyatkin, V. V. Rusakova, R. Z. Stanoyeva
Joint Institute for Nuclear Research, Dubna, 141980, Russia
arXiv:1411.5806v1 [nucl-ex] 21 Nov 2014
The charge topology of the events of coherent dissociation of 11 C and 12 N of an energy of 1.2 A GeV
in nuclear track emulsion is presented and its compared is given with the appropriate data on the
nuclei 7 Be, 8,10 B, 9,10 C and 14 N.
Light nuclei, are represented as virtual superpositions of lighter core nuclei, the lightest cluster nuclei (α-particle,
triton, 3 He nucleus or helion, deuteron) and nucleons, which coexist in a balance. This variety makes the group of
nuclei at the beginning of the table of isotopes a nuclear clustering “laboratory”. The study of the 11 C nucleus is of a
fundamental importance due to the combination of cluster and shell features in it. The isotope 11 C is a link between
stable nuclei with a pronounced α-particle clustering of nucleons and nuclei at the boundary of proton stability, where
clustering based on the isotope 3 He is not less important. Interactions of clusters and exchange by a neutron between
them result in the formation of structures with a core nucleus along with the 3-cluster configuration 24 He + 3 He. The
weakly bound configurations 7 Be + α (7.6 MeV), 10 B + p (8.7 MeV) and 3 He + 8 Be (9.2 MeV) are more expected,
and 9 B + d (14.9 MeV), 9 Be + 2p (15.3 MeV) and 8 B + t (27.2 MeV) are less expected.
A balanced co-existence of these modes determines the properties of the 11 C ground state. The fact of its bondage
is important for understanding light isotope abundances. The 11 C isotope can be synthesized in a mixture of isotopes
3
He and 4 He either through the 7 Be or 8 Be followed by a partial clustering into 10 B + p. The decay of 11 C leads
to the formation of a stable isotope 11 B observed in cosmic rays. Such a scenario is not recognized – isotopes 10,11 B
are considered as products of bombardment of carbon stars surfaces by high-energy protons. Observations of the
7
Be + α and 3 He + 8 Be dissociations will confirm the existence of states genetically related to the 11 C synthesis.
Understanding of the 11 C structure is required for the interpretation of the existing data for 12 N and, potentially, for
13
O in which 11 C plays the role of core. In rapid processes of nucleosynthesis (“hot break outs”), these isotopes act
as genetically related “waiting stations”. The formation of the 12 C isotope or heavier ones can proceeds through them
by attaching of protons. It is worth to notice that knowledge of the relativistic 11 C fragmentation is indispensable for
the application of intense beams of these nuclei in nuclear medicine.
The cluster structure of light nuclei is studied in relativistic fragmentation processes by nuclear track emulsion
(NTE) methods in the framework of the BECQUEREL Project at the JINR Nuclotron [1-11]. Development of the
research and illustrations are presented in the review [12]. Among the events of the relativistic nucleus fragmentation,
the events of coherent dissociation in narrow jets of fragments are particularly valuable for the study of the clustering
of nucleons. They have neither tracks of slow fragments of target nuclei nor mesons. This feature reflects a minimum
excitation of the relativistic nucleus under investigation in a “glancing” collision with a heavy nucleus from the NTE
composition. The mechanism of coherent dissociation in NTE is a nuclear diffraction interaction [13] occurring without
angular momentum transfer.
The experimental approach is based on a record spatial resolution and sensitivity of NTE, the layers of which are
exposed longitudinally to the beams of relativistic nuclei. It has already provided obtaining of wholesome information
regarding the aspects of the cluster structure of the family of light nuclei including radioactive ones. One of the key
nuclei – 11 C – was found to be missed due to circumstances of a practical nature. Filling of this gap is the motivation
to start a new cycle of research on the BECQUEREL Project. The methods of analysis of 11 C are to be rather
complex due to existence of many possible configurations.
The coherent dissociation events got a short name of the “white” stars due to the absence of strongly ionizing
particle tracks. The name well reflects a sharp “breakdown” of the ionization density in the vertex of the interaction
in the transition from the primary nucleus track to a narrow cone of secondary tracks. This feature is a fundamental
difficulty for electronic methods, because the larger the degree of dissociation in the event, the harder to register it.
On the contrary, such events in NTE are observed and interpreted in the most obvious way, and their distribution via
the interactions with different compositions of charged fragments are determined fully exhaustively. This probability
distribution is a main observed characteristic of the cluster structure of the nucleus in question.
The distributions over the probability of finite configurations of fragments in “white” stars allow one to reveal their
contributions to the structure of the studied nuclei. It is assumed that a specific configuration is fixed at dissociation
randomly, without sampling, and the dissociation mechanism does not lead to sampling of such states through the
3
FIG. 1: Amplitude spectrum from a scintillation counter when transporting nuclei
12
C (arbitrary units)
FIG. 2: Amplitude spectrum from a scintillation counter when transporting nuclei
11
C (arbitrary units)
The reduced thickness and the glass substrates of an experimental batch of NTE do not enable one to perform
analysis with scanning along beam and secondary tracks without sampling. Therefore, scanning of the NTE layer
was carried out on transverse strips in order to the find tracks of relativistic fragments with the total charge of at
least 3 with a subsequent viewing up to the interaction vertices. Tracks corresponding to doubly and singly charged
relativistic particles are determined visually. Dominance of C nuclei in the beam makes possible to specify charges of
heavier fragments in “white” stars as values that does not reach six charge units.
Table 3. Distribution over charge channels for the ”white” stars produced by carbon isotopes.
Channel
B+H
Be + He
Be + 2H
3He
2He + 2H
He + 4H
Li + He + H
Li + 3H
6H
11
C
6 (5 %)
17 (14 %)
22
60
14
4
(18 %)
(48 %)
(11 %)
(3 %)
3 (2 %)
10
C [9]
1 (0.4 %)
6 (2.6 %)
12 (5.3 %)
186 (82 %)
12 (5.3 %)
1 (0.4 %)
9 (4 %)
9
C [5]
15 (14 %)
16
16
24
28
(15
(15
(23
(27
%)
%)
%)
%)
2 (2 %)
6 (6 %)
By the present time 126 “white” stars with a total charge of relativistic fragments equal to 6 are found in six scanned
layers. Their distribution over charge states is given in Table. 3. Table. 3 also contains data on the isotopes 10 C [9]
and 9 C [5], which indicate a specific nature of a “white” star distribution of each of the isotopes and the compliance
of the performed exposures to the mass numbers of the C isotopes. In the study of the coherent dissociation of
relativistic 12 C nuclei [17] all 100 “white” stars are found in a single channel 12 C → 3He clearly reflecting the 3αparticle clustering of this nucleus. The decays of unbound relativistic 8 Be nuclei the contribution which was about
20% became the key observation.
Events containing only the relativistic isotopes of He and H (77%), in particular, 2He + 2H dominate among the
11
C “white” stars. The ratio of the statistics of this channel to the statistics of the channel He + 4H is 6 ± 3. It does
not correspond to the idea about the only dissociation of the 7 Be core mentioned above. In contrast to the previously
studied neutron deficient nuclei one can see a significant fraction of events Li + He + H is observed, which could
correspond to 6 Li + 4 He + p. There are no events Be + 2H which could correspond to 9 Be + 2p. However, there
is a significant fraction of Be + He events. If the 4 He isotope is identified in them the isotope 7 Be is determined