1. Qiang Zhao Institute of High Energy Physics, CAS and Theoretical Physics Center for Science Facilities (TPCSF), CAS zhaoq@ihep.ac.cn Surprises from charmonium decays Institute of High Energy Physics, CAS 第九届全国重味物理和 CP 破坏研讨会， 2011 年 10 月 12-16 日，杭州

2. Outline 1. Charmonium and charmonium-like states 2. Direct evidence for open charm threshold effects in e + e -  J/ , J/   0, and  c 3. Puzzles in charmonium decays 4. Summary

3. New charmonium-like states, i.e. X, Y, Z’s, are observed in experiment Do not fit in the conventional charmonium spectrum as quark-antiquark states. Most of these new states, such as X(3872), are located close to a two-particle threshold. Evidence for charged charmonium states, e.g. Z(4430). Good candidates for hadronic molecules or other non- standard configurations, e.g. tetraquarks, hybrids, etc. Greatly enrich our knowledge about strong QCD. Recent experimental progress

4. Charged charmonium spectrum -- A completely new scenario of strong QCD! States close to open thresholds -- The role played by open D meson channels? Close to D  D* threshold c L S=0,1 cc J=L+S

5. 1010.5827 [hep-ph]

6. new CDF meas. new Belle meas. M D0 + M D*0 3871.8±0.4 MeV = 3871.46 ± 0.19 MeV  m =  0.35 ± 0.41 MeV Observation of X(3872) The mass of X(3872) does not fit in (c  c) 1 ++ state of quark model Small mass difference to D  D* threshold Large isospin-violating decay modes J PC = 2  is not ruled out

7. A good candidate for hadronic molecule (Tornqvist 1991) u u d d u d d d d u  Proton Neutron Deuteron: p-n molecule Nature of X(3872) The compositeness criterion can be applied Tremendous contributions from theory commu. A B C. Z B X =  0.35 ± 0.41 MeV

8. Charged charmonium-like states Resonant structure Z(4430) –Close to D *   D 0 1 threshold –Q =  1, J P = 0 ,1 ,2  –M= 4433 MeV –  = 45 MeV S.K. Choi et al., PRL 100,142001 (2008) First direct evidence for an exotic quark configuration, i.e. (c  c u  d).

9. arXiv:1105.4583[hep-ex]

10. Look for direct evidence for open charm threshold effects: 1) Spectrum studies 2) Production and decay processes (e.g. e + e -  J/ , J/   0,  c )

11. 1010.5827[hep-ph] X(3900) Close to D  D* threshold

12. 1 ,  … ** e+e+ ee Direct production of vector charmonium states Dynamics for charmonium interactions with final states Signals for exotics? X(3900)? … Belle, BaBar, and BEPC-II i) Charmonium production in e  e     final particles

13. Pakhlova et al., Belle Colla., PRD77, 011103(2008). Y.-J. Zhang and Q. Zhao, PRD81, 034011 (2010)  (3770), 1D  (4040), 3S  (4160)  (4415) X(3900) ? What is X(3900)? Not inlcuded in PDG2010. Not in charmonium spectrum … … e+e-  D  D Open charm effects in the cross section lineshape studies

14. Y.J. Zhang and QZ, PRD81, 034011 (2010) e+e-  D  D* + c.c. e+e-  D  D D  D* open threshold may explain:

15. ii) Direct evidence for open charm effects in e  e   J/  , J/   0  (3770) J/  (I=0)  (I=0) D0D0 D0D0 D* 0 (I=0)  0 (I=1) If m u = m d,  m(D 0 ) = m(D  ) (a) + (b) = 0 If m u  m d,  m(D 0 )  m(D  ) (a) + (b)  0 DD DD D*  (a)(b)  0 (I=1) For the isospin-violating J/  0 production:

16. Cross section lineshape of e + e   J/  

17. Direct evidence for open charm effects in the cross section lineshape of Wang, Liu, Zhao, 1103.1095[hep-ph], PRD84, 014007(2011) e + e   J/   0 ~ 8 MeV

18. Possible further evidence for open charm effects in the cross section lineshape of e + e    c

19. “  puzzle” in J/ ,   VP decay  (3770) non-D  D decay M1 transition problem in J/ ,     c, (   c ) Recent puzzling results for J/ ,    ,   Large  c (  c )  VV branching ratios Decays of  c1  VV and  c2  VP Isospin-violating decay of  (3770) and   J/   0, and h c  0 Could be more … … Conjecture: 1)These puzzles could be related to non-pQCD mechanisms in charmonium decays due to intermediate D meson loops. 2)The intermediate meson loop transition could be a mechanism for the evasion of the helicity selection rule. Puzzles in charmonium decays

20.  “  - 疑难 ” 和  (3770) 的非 D 介子衰变 c J/ ,  ' g c cc ** cc QCD 理论可以在 J/  和  衰变之间建立起一个简单的关系： J/ ,   衰变严重 偏离这一 “12% 法则 ” ： R(  ) =  0.2 % 强衰变 电磁衰变

21. c  (3770) g cc 强衰变 非 D 介子对 实验观测的矛盾： BES-II 发现  (3770) 的非 D 介子对衰变分 支比约为 15% ；而 CLEO-c 发现这一衰变 分支比几乎可以忽略（上限约为 9% ）。 微扰 QCD 理论计算发现： [He, Fan, and Chao, PRL101, 112001 (2008)] 非相对论 QCD 领头阶的计算与 CLEO-c 的结果一致，但是次领头阶的修正 却极为重要，可以给出约为 5% 的分支比。 暴露出的问题： QCD 非微扰机制在粲偶素能区可能变得极为重要！

22. J/  (3096)  (3686)  (3770) D  D 衰变阈 J PC = 1    (3686) c cc (ud)(ud) (du)(du) D  D 衰变阈会通过与 “ 非淬火 ” 效应相关的 D 介子圈影响  (3686) 的衰变 性质，特别是压低   的强衰变振幅强度；同时导致  (3770) 的非 D 介子对衰变的非微扰跃迁。 D DD c cc  (3770) D(c  q)  D(q  c)  (3770) c cc (ud)(ud) (du)(du) D DD

23.  (3770) 通过 D 介子圈衰变到非 D 介子对末态的 非微扰跃迁机制 Y.-J. Zhang, G. Li and Q. Zhao, Phys. Rev. Lett. 102, 172001 (2009) 可以合理解释  (3770) 较大的非 D 介子衰变分支比！

24. Open-charm effects as an OZI-rule evading mechanism J/  (  ) c cc V D DD D* Interferences among the single OZI, EM and intermediate meson loop transitions are unavoidable.  Mechanism suppressing the strong decay amplitudes of   VP c c* V P g P J/  (  ) SOZI: pQCD dominant OZI-evading: non-pQCD dominant

25. J/  (  )   t-channel J/  (  )   V     s-channel Decomposition of OZI evading long-range loop transitions D DD DD D D*  … … Zhang, Li and Zhao, 0902.1300[hep-ph]; Li and Zhao, PLB670, 55(2008)

26. Recognition of interferences Property of the anti-symmetric tensor coupling allows a parametrization: Zhao, Li, and Chang, JPG2009 In order to account for the “  puzzle”, a destructive phase between andis favored. Overall suppression of the  strong decay coupling:

27. Preliminary results

28. The same mechanism should contribute in various processes involving the same charmed meson loops

29. Nonrelativistic quark model: Isgur et al. GI: Godfrey and Isgur Lattice results: Dudek et al., PRD79, 094504 (2009) Li and Zhao: PLB670, 55 (2008); PRD84, 074005 (2011)

30. Surprises from higher charmonium states could be signals for nonperturbative mechanisms due to open charms. Open charm effects could be essential for understanding some of those long-standing puzzles in charmonium decays  (3770) non-D  D decays “  puzzle” in J/ ,  ’  VP M1 transition problem in J/ ,     c, (   c ) Isospin violating decay of  and  (3770)  J/  0 Helicity selection rule violations (  c1  VV,  c2  VP,  c  B  B …) Cross section lineshapes of e+e-  D  D and D  D*+c.c. … Lots of opportunities for experiments accessible this energy region, such as BES-III, Panda, Super-B … Summary

31. 1)Look for systematic constraints on the model uncertainties in all relevant processes. 2)Look for effects of hadronic loop contributions as unquenched effects in charmonium spectrum (refs.: T. Barnes and E. Swanson, PRC77, 055206 (2008); Li, Meng and Chao, PRD80, 014012(2009) 3) Compare different theoretical approaches, e.g. NREFT and ELA in isospin-violating charmonium decays. (refs.: Guo, Hanhart, and Meissner, PRL(2009); Guo, Hanhart, Li, Meissner, QZ, PRD(2010); and PRD(2011).) To firm up open charm effects …

32. Part of relevant references: 1.G. Li and Q. Zhao, Phys. Rev. D 84, 074005 (2011), arXiv:1107.2037[hep-ph]. 2.Q. Wang, X.-H. Liu and Q. Zhao, Phys. Rev. D 84, 014007 (2011). 3.Q. Zhao, Phys. Lett. B 697, 52 (2011). 4.F.-K. Guo, C. Hanhart, G. Li, Ulf-G. Meißner, Q. Zhao, Phys. Rev. D 83, 034013 (2011); arXiv:1008.3632[hep-ph]. 5.X.-H. Liu and Q. Zhao, J. Phys. G 38, 035007 (2011); arXiv:1004.0496 [hep- ph]. 6.F.-K. Guo, C. Hanhart, G. Li, Ulf-G. Meißner, Q. Zhao, Phys. Rev. D 82, 034025 (2010); arXiv:1002.2712[hep-ph]. 7.X.-H. Liu and Q. Zhao, Phys. Rev. D 81, 014017 (2010) 8.Y.J. Zhang, G. Li and Q. Zhao, Phys. Rev. Lett. 102, 172001 (2009); arXiv:0902.1300 [hep-ph]. 9.Y.-J. Zhang and Q. Zhao, Phys. Rev. D81, 034011 (2010) 10.Y.J. Zhang and Q. Zhao, Phys. Rev. D 81, 074016 (2010) 11.Q. Zhao, G. Li and C.H. Chang, Chinese Phys. C 34, 299 (2010); 12.G. Li and Q. Zhao, Phys. Lett. B 670, 55(2008). 13.G. Li, Q. Zhao and C.H. Chang, J. Phys. G 35, 055002 (2008) 14.Q. Zhao, G. Li and C.H. Chang, Phys. Lett. B 645, 173 (2007)

33. Thanks for your attention!

34. Anomalously large isospin violations: Theoretical interpretation: Wu, Liu, Zhao and Zou, arXiv: 1108.3772[hep-ph] Triangle singularitya0-f0 mixing BESIII@Hadron2011

35. Direct test of rho-pi puzzle: J/ ,   PP for the role played by EM annihilations (X.Q. Li)  c,  c  VV for the role played by strong annihilations (Wang, Liu, QZ) Indirect tests: Helicity selection rule violation processes and correlations with the OZI rule violations (Liu et al; Liu, Wang, QZ) Strong isospin violations via charmed meson loops (Guo, Hanhart, Li, Meissner, QZ) Open charm effects in the cross section lineshape studies B meson loops in Upsilon decays (Chao et al) Open threshold effects on the charmed meson spectrum (Barnes et al; Chao and Meng) To pin down the underlying dynamics