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1
Recent Bottomonium Results
from BaBar and Belle
Veronique Ziegler (SLAC)
Representing the BaBar Collaboration
13th International Conference on B-Physics
at Hadron Machines
Amsterdam, 4 – 8 April 2011
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U(nS) Data Sets
Samples (1S) (2S) (3S)
BaBar
Belle
(4S)
14 fb-1 30 fb-1 433 fb-1
6 fb-1 24 fb-1
3 fb-1
711 fb-1
(5S)
3.2 fb-1 (scan)
121 fb-1
s
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Radiative transition studies
from inclusive spectra for
converted photons
• U(2S, 3S) data samples
4
Radiative bottomonium transitions from
U(3S) events using g→e+e- conversions
Reconstructed Vertices
Energy in C.M. frame
Significantly improves energy resolution
Efficiency ~(0.1 – 1)%
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Inclusive photon energy regions for U(3S) events
Eg(i ) 
mi2 - m 2f
2mi
 [207,243] MeV
•Resolution dominated
•Small Doppler broadening

b0
 bJ (2 P )  g U (2 S )
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Inclusive photon energy regions for U(3S) events
Eg(i ) 
Eg(i ) 
mi2 - m 2f
2mi
mi2 - m 2f
2mi
 [430,484] MeV
 [391,442] MeV
from U(3S)
to U(1S)
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Inclusive photon energy regions for U(3S) events
Search for the Bottomonium Ground State hb(1S)
Eg 
(i )
mi2 - m 2f
2mi
 [743,777] MeV
U(3S)→ g hb(1S)
photons from
calorimeter

hb significance < 3s
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Inclusive photon energy regions for U(3S) events
Search for the Bottomonium Ground State hb(1S)
Eg 
(i )
mi2 - m 2f
2mi
 [743,777] MeV
hb significance < 3s
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Inclusive photon energy regions for U(2S) events
Eg 
(i )
mi2 - m 2f
2mi
 [391,442] MeV
hb significance < 3s
ISR
hb (1S)
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Inclusive photon energy regions for U(2S) events
hb significance < 3s
Eg 
(i )
mi2 - m 2f
2mi
 [391,612] MeV
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Summary of BF measurements from U(2S,3S)
radiative decays using converted photons
• Precise measurements of
bJ(nP) n=1,2 → g U(mS)m=1,2 BFs
• Good agreement with theory
(e.g. Kwong & Rosner, PRD38, 279
(1988))
• Measurements of BFs for
U(3S)→ g bJ(1P) transitions
-- transition to b1(1P) not seen
 in general inconsistent with
theoretical predictions
?
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The search for the hb(1P) state
in U(3S) data
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Hyperfine splitting for L=1 states
M [c.o.g.(13PJ)] – M(11P1)
M HF (nL) 
M ( n 3 LJ )
- M (n1 LJ  L ) ~ 0

J ( 2 J +1) M J / J ( 2 J +1)


 M (11 P1 ) ~ M (13 P0 ) + 3M (13 P1 ) + 5M (13 P2 ) / 9  9.89987  0.00027 GeV/c 2
U(3S)
bJ(1P)
hb(1P)
Search for a
peak in invariant
mass of system
recoiling against
p0 or p+p
mrecoil ( X )  ( EU* (3S ) - E X* ) 2 - ( p*X ) 2
hb(1S)
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Evidence for the hb(1P) in the decay U(3S) pohb
arXiv:1102.4565
• 9145 ± 2804 signal events
• M(hb) = 9902+/-4(stat) +/-1(syst) MeV/c2
 consistent with predictions
• Stat. Signif = 3.2s i.e. √2, including
systematic errors = 3.0s (evaluated with
the hb mass fixed at expected value of 9.9
GeV/c2)
•
•
B(U(3S)p0hb(1P) = (3.7±1.1±0.4)10-4
B(U(3S)p0hb(1P)< 5.810-4 (@ 90% CL)
background-subtracted result:
yield as a fcn of assumed hb mass:
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Search for the hb(1P) in the decay U(3S)p+p-hb
background-subtracted result:
hb ?
U (3S )  p +p - U (2 S )
U (3S )  X U (2 S )  p p U (1S )
+
-
K S0  p +p -
 b1.2 (2 P)  p +p -  b1.2 (1P)
•
No hb observation: -1106 ± 2432(stat.) signal events
(mass fixed at 9.9 GeV/c2)
• BF(U(3S)p+p-hb)<1.0x10-4 (@90% C.L.)
--suppressed by a factor >3 compared to p0 mode
• BFs improved w.r.t. current PDG values:
-- BF(U(3S)p+p-U(2S))=(3.00 ± 0.02 ± 0.14)%
-- di-pion transition between bJ states
-- BF(U(3S)X(U(2S)p+p-U(1S))=(1.78±0.02±0.11)%
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The search for the hb(nP) states
in U(5S) data
Expected mass :
M hb (1P)  9899.87  0.17  0.31 MeV/c 2
M hb (2 P)  10260.24  0.15  0.50 MeV/c 2
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Motivation to take data at the U(5S) resonance
•Studies of Bs decays
2 orders of
magnitude
larger
indicate
stronger
coupling
•Anomalous production of
U(nS)n=1,2,3p+p•Possibly explained by the
presence of exotic resonance
Yb, bottomonium analog of
charmonium Y(4260),
responsible for high transition
rates
•Belle scan of the Y(5S) region to
search for the Yb
─ discrepancy between
U(nS)p+p- cross section
lineshape and hadronic cross
section (BaBar) at the 2s level
─ B(U(5S)→BB*p)=(7.3+2.3
-2.1 ±0.8)%
> one order of magnitude larger
than expected
?
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Measured e+e- →p+p- MM transitions at U(5S) energy
arXiv:1103.3419
Observation of the hb(1P)
and hb(2P) states
background-subtracted results
• Signal
lineshapes
from calibration channels
U(5S)→U(nS) p+p→m+m-
• measured hb(1P,2P) mass values
consistent with calculated values
• no info. on p0 transitions as yet
• observed hb production rate
enhancement may be indicative
of exotic process violating HQ
spin-flip suppression
• hb not seen in U(4S) data
Conclusions
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• Bottomonium Spectroscopy at the U(2S, 3S)
─ Precision measurements of radiative transitions between known
bottomonium states using g → e+ e─ Searches for predicted states
─ BaBar: Evidence for U(3S)→ p0 hb(1P)
arXiv:1102.4565
No evidence for U(3S)→ p+p- hb(1P)
• Bottomonium Spectroscopy at the U(5S)
─ Belle: observation of the hb(1P) and hb(2P) states
arXiv:1103.3419
─ Measured mass values consistent with C.o.G. of partner bJ states
─ Unexpectedly large production rates
─ Possibility for the existence of a Yb exotic bottomonium candidate, the
analog of the Y(4260) in the charmonium sector
TOPICS COVERED ELSEWHERE
•Bottomonium Spectroscopy above the U(4S) targeted for studies of Bs decays
─ Belle: observation of Bs→J/y f0(980) and evidence for Bs→J/y f0(1370)
arXiv:1102.2759
─ BaBar: measurement of inclusive BF for Bs→X l nl and Bs production rate