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Study of  c Decays at BES

Study of  c Decays at BES. Zijin Guo University of Hawaii (Representing BES Collaboration) Quarkonium Working Group ’04, IHEP Beijing October 13, 2004. OUTLINE Introduction  cJ  pp,   cJ  h + h - KsKs  cJ  K * (892) 0 K * (892) 0  c0  f 0 (980)f 0 (980)

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Study of  c Decays at BES

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

  2. OUTLINE • Introduction • cJ  pp,  • cJ  h+h-KsKs cJ  K*(892)0K*(892)0 c0  f0(980)f0(980) • c2 polarization • Summary   

  3. INTRODUCTION Charmonium System

  4. Exclusive quarkonium decays contribute an important laboratory for investigating QCD. • Compared to J/ decays, relatively little is known concerning PC = ++ cJdecays. • 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

  5. World (2S) Samples (×106) Largest from BES (2S) 2002 BESII Detector

  6.  cJ  pp,  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 singlet graphs (qq) for CJ → . Coloroctetgraphs (qqg)

  7. cJ   (2S)  cJ  ΛΛ  p-p+ Monte Carlo  Data Clear Λ Λ-bar signal

  8. cJ signal Data/Monte Carlo c1 c0 c2 Sideband background +1.3 +1.0 +1.5  -1.2 -0.9 -1.3 PRD67, 112001 (2003)

  9. cJ  pp Final states: pp c0 c1 c2

  10. COM for cJB B Discussion Calculate Many systematic errors cancel! • The results on c1 and c2 decays only agree marginally with model predictions. • No prediction for c0 . Phys.Rev.D69:092001,2004

  11. cJ  h+h-KsKs (2S)  cJ cJ → KSKS cJ → +-KSKS BESII Preliminary cJ → K+K-KSKS

  12. 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.

  13. cJ  K*(892)0K*(892)0 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. (2S)→ +-K+K-

  14. K*(892) significance = 4.7σ, 4.5σ, 7.6σ c0 c1 c2 Accepted by Phys. Rev. D, hep-ex/0408012

  15. c0  f0(980)f0(980) 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 ?

  16. c0 → +-+- c2 → +-+- f0f0

  17. Plot mass recoiling from f0(980) f0 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 Accepted by PRD, hep-ex/0406079

  18. c2 polarization in (2S)  c2, c2  +-, K+K- • 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).

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

  20. 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.

  21. combine them, : correlation factor quadrapole amplitude a2´ (CB) octupole amplitude a3´ +- K+K- consistent with the pure E1 transition well good agreement is observed in all angular distributions Accepted by PRD, hep-ex/0409034

  22. SUMMARY    • 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 statesandtest 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…

  23. Thank you 谢谢

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