Study of c Decays at BESZijin GuoUniversity of Hawaii(Representing BES Collaboration)

Quarkonium Working Group 04, IHEP BeijingOctober 13, 2004

OUTLINE

Introduction cJ pp, cJ h+h-KsKs cJ K*(892)0K*(892)0 c0 f0(980)f0(980) c2 polarization Summary

INTRODUCTIONCharmonium 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)

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) forCJ .cJ pp,

(2S) cJ p-p+Clear -barsignalMonte CarloDatacJ

+1.3-1.2+1.0-0.9+1.5-1.3PRD67, 112001 (2003)Sideband backgroundData/Monte CarlocJ signalc0c1c2

c0c1c2BcJ (10 4)4.7 1.02.6 0.63.3 0.7

c0c2c1Final states: ppcJ pp

COM for cJ B BDiscussionMany 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 KSKScJ +-KSKSBESII PreliminarycJ h+h-KsKs(2S) cJcJ K+K-KSKS

BESII 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 betterunderstand P-wave decays.

Study cJ K*(892) K*(892) K+K-+-Require Prob(24C) > 1% andhigher 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 = 4.7, 4.5, 7.6 c0c1c2

f0(980) controversial:

Even mass and width complicatedby KK threshold.Experimental results needed.Study (2S) c0 f0f0 +-+-Require Prob(24c) > 1%. qq-bar meson?KK-bar molecule?multiquark state?glueball ?c0 f0(980)f0(980)

c0 +-+-c2 +-+-f0f0

ResultsN = 65 51/1.75 = 35.9 9.0 significance = 4.6 = (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 recoilingfrom 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 multipolesS- 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 a2octupole amplitude a3consistent 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 BESIIs 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

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