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Zijin Guo University of Hawaii (Representing BES Collaboration) Quarkonium Working Group ’04, IHEP Beijing October 13, 2004 Study of c Decays at BES

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

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INTRODUCTION Charmonium System

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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

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World (2S) Samples (×10 6 ) (2S) BESII Detector

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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,

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(2S) cJ ΛΛ p - p + Clear Λ Λ-bar signal Monte Carlo Data cJ

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c0 c1 c2 B cJ (10 –4 )4.7 ± ± ± PRD67, (2003) Sideband background Data/Monte Carlo cJ signal c0 c1 c2c2

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c0 c2 c1 Final states: pp cJ pp

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COM for cJ B B Discussion 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

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cJ → K S K S cJ → + - K S K S BESII Preliminary cJ h + h - KsKs (2S) cJ cJ → K + K - K S K S

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BESII Preliminary The branching fractions of cJ decays to + - K S K S and K + K - K S K S are observed for the first time. The branching fractions of c0 and c2 decays to K S K S are measured with improved precision.

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Measure more decays to better understand P-wave decays. Study χ cJ → K * (892) K * (892) → K + K - + - Require Prob( 2 4C ) > 1% and higher than + - + - and K + K - K + K - cases, and PID imposed. cJ K * (892) 0 K * (892) 0 (2S) → + - K + K -

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Accepted by Phys. Rev. D, hep-ex/ K * (892) significance = 4.7σ, 4.5σ, 7.6σ c0 c1 c2

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f 0 (980) controversial: Even mass and width complicated by KK threshold. Experimental results needed. Study (2S) → χ c0 → f 0 f 0 → + - + - Require Prob( 2 4c ) > 1%. qq-bar meson? KK-bar molecule? multiquark state? glueball ? c0 f 0 (980)f 0 (980)

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c0 → + - + - c2 → + - + - f0f0f0f0

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Results N = 65 – 51/1.75 = 35.9 ± 9.0 significance = 4.6σ ε = (3.92 ± 0.07)% B( (2S) → c0 → f 0 f 0 → + - + - ) = (6.5 ± 1.6 ± 1.3) x B( c0 → f 0 f 0 → + - + - ) = (7.6 ± 1.9 ± 1.6) x f0f0 Accepted by PRD, hep-ex/ Plot mass recoiling from f 0 (980)

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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 polarization in (2S) c2, c2 + -, K + K -

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No background from c1 since the c1 + -, K + K - processes are forbidden by parity conservation.

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The helicity amplitudes are determined by a maximum likelihood fit to the angular distribution, where x=A 1 /A 0, y=A 2 /A 0, A 0,1,2 are the c2 helicity amplitudes.

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good agreement is observed in all angular distributions + - K+K-K+K- combine them, quadrapole amplitude a 2 ´ octupole amplitude a 3 ´ consistent with the pure E1 transition well : correlation factor (CB) Accepted by PRD, hep-ex/

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c decays to pp, , h + h - KsKs, K *0 K *0 and f 0 (980)f 0 (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

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Thank you 谢谢

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