Near Threshold Heavy Quarkonium Photoproduction at Large ...
Zijin Guo University of Hawaii (Representing BES Collaboration) Quarkonium Working Group ’04, IHEP...
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Transcript of Zijin Guo University of Hawaii (Representing BES Collaboration) Quarkonium Working Group ’04, IHEP...
Zijin Guo
University of Hawaii(Representing BES Collaboration)
Quarkonium Working Group ’04, IHEP Beijing
October 13, 2004
Study of c Decays at BES
OUTLINE
• Introduction
• cJ pp,
• cJ h+h-KsKs
cJ K*(892)0K*(892)0
c0 f0(980)f0(980)
• c2 polarization
• Summary
INTRODUCTION
Charmonium System
• Exclusive quarkonium decays contribute an important laboratory for investigating QCD.
• Compared to J/ decays, relatively little is known concerning PC = ++ cJ decays.
• Color octet mechanism (COM) important for P-wave quarkonium decays.
A consistent set of theoretical predictions for the branching fractions, as well as more precise experimental measurements will lead to a better understanding of the COM and the nature of cJ states.
• Furthermore, the decays of cJ , in particular c0 and c2, provide a direct window on glueball dynamics in the 0+
+ and 2++ channels. C. Amsler and F. Close, PRD53 (1996) 295
World (2S) Samples (×106)
(2S)
0
2
4
6
8
10
12
14
MKI MKII MKIII CBAL BESI BESII CLEO
BESII Detector
Color octet mechanism (COM) important for P-wave quarkonium decays.
G. T. Bodwin et al., Phys Rev. Lett. D51, 1125 (1995).H.-W. Huang and K.-T. Chao, Phys. Rev. D54, 6850 (1996).J. Bolz et al., Phys. Lett. B392, 198 (1997).
Color octet graphs (qqg)
Color singlet graphs (qq) for
CJ → .
cJ pp,
(2S) cJ ΛΛ p-p+
Clear Λ Λ-barsignal
Monte Carlo
Data
cJ
c0 c1 c2
BcJ
(10 –4) 4.7 ± 1.0 2.6 ± 0.6 3.3 ± 0.7+1.3-1.2
+1.0-0.9
+1.5-1.3
PRD67, 112001 (2003)
Sideband background
Data/Monte Carlo
cJ signal
c0
c1 c2
c0
c2
c1
Final states: pp
)10( 4 0c1c 2c
)( ppB cJ )04(PDG 27.024.2 13.072.0 07.068.0
)( ppB cJ 47.071.2 43.039.0
09.057.0 17.015.0
10.065.0 24.021.0
cJ pp
0c1c 2c
BESRB 63.073.1
598.0
08.308.5
449.0
34.256.4
COM for cJ B B
Discussion
COMRB
Many systematic errors cancel!
Calculate
• The results on c1 and c2 decays only agree marginally with model predictions. • No prediction for c0 .
Phys.Rev.D69:092001,2004
cJ → KSKS
cJ → +-KSKS
BESII PreliminaryBESII Preliminary
cJ h+h-KsKs
(2S) cJ
cJ → K+K-KSKS
BESII PreliminaryBESII Preliminary
The branching fractions of cJ decays to +-KSKS and
K+K-KSKS are observed for the first time.
The branching fractions of c0 and c2 decays to KSKS are measured with improved precision.
Measure more decays to better
understand P-wave decays.
Study χcJ → K*(892) K*(892)
→ K+K-+-
Require Prob(24C) > 1% and
higher than +-+- and K+K-K+K-
cases, and PID imposed.
cJ K*(892)0K*(892)0
(2S) → +-K+K-
Accepted by Phys. Rev. D, hep-ex/0408012
K*(892)
significance = 4.7σ, 4.5σ, 7.6σ
c0 c1 c2
f0(980) controversial:
Even mass and width complicated
by KK threshold.
Experimental results needed.
Study (2S) → χc0
→ f0f0 → +-+-
Require Prob(24c) > 1%.
• qq-bar meson?
• KK-bar molecule?
• multiquark state?
• glueball ?
c0 f0(980)f0(980)
c0 → +-+- c2 → +-+-
f0f0
Results
N = 65 – 51/1.75 = 35.9 ± 9.0 significance = 4.6σ
ε = (3.92 ± 0.07)%
B((2S) → c0 → f0f0 → +-+-) = (6.5 ± 1.6 ± 1.3) x 10-5
B(c0 → f0f0 → +-+-) = (7.6 ± 1.9 ± 1.6) x 10-4
f0
Accepted by PRD, hep-ex/0406079
Plot mass recoiling
from f0(980)
• In general, it is believed that (2S) cJ is dominated by the E1 transition, but with some M2 (for c1 and c2) and E3 contributions (for c2).
• The calculated pure E1 transition rates and the experimental results are quite different.
Determine the contributions of the higher multipoles
• S- and D-wave mixing of (2S) and (3770) may be the key to solve the long-standing puzzle and to explain (3770) non-DD decays.
• Crystal Ball studied the decay angular distributions in (2S) c2 using (2S) J/ first; no significant higher multipoles found (with limited statistics).
c2 polarizationin (2S) c2, c2 +-, K+K-
No background from c1 since the c1 +-, K+K-
processes are forbidden by parity conservation.
The helicity amplitudes are determined by a maximum likelihood fit to the angular distribution, where x=A1/A0, y=A2/A0, A0,1,2 are the c2 helicity amplitudes.
good agreement is observed in all angular distributions
+-
K+K-
combine them,
quadrapole amplitude a2´
octupole amplitude a3´
consistent with the pure E1 transition well
: correlation factor
(CB)
Accepted by PRD, hep-ex/0409034
c decays to pp, , h+h-KsKs, K*0K*0 and f0(980)f0(980) are measured for the first time or with higher sensitivity using BESII’s 14 million (2S) data sample.
helpful to better understand the nature of c states and test the new QCD approach.
• The helicity amplitudes of (2S) c2 are measured for
c2 +- and K+K-, and x = 2.08 0.44, y = 3.03 0.66 with correlation = 0.92 are obtained.
in good agreement with a pure E1 transition
• More experimental facts are desired
Theoretical predictions…
SUMMARY
Thank you
谢谢