Qiang Zhao Institute of High Energy Physics, CAS and Theoretical Physics Center for Science Facilities (TPCSF), CAS 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 日，杭州

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

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

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

[hep-ph]

new CDF meas. new Belle meas. M D0 + M D* ±0.4 MeV = ± 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

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

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, (2008) First direct evidence for an exotic quark configuration, i.e. (c  c u  d).

arXiv: [hep-ex]

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 )

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

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

Pakhlova et al., Belle Colla., PRD77, (2008). Y.-J. Zhang and Q. Zhao, PRD81, (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

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

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:

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

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

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

“  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

 “  - 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

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, (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！

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

 (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, (2009) 可以合理解释  (3770) 较大的非 D 介子衰变分支比！

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

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, [hep-ph]; Li and Zhao, PLB670, 55(2008)

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:

Preliminary results

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

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

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

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, (2008); Li, Meng and Chao, PRD80, (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 …

Part of relevant references: 1.G. Li and Q. Zhao, Phys. Rev. D 84, (2011), arXiv: [hep-ph]. 2.Q. Wang, X.-H. Liu and Q. Zhao, Phys. Rev. D 84, (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, (2011); arXiv: [hep-ph]. 5.X.-H. Liu and Q. Zhao, J. Phys. G 38, (2011); arXiv: [hep- ph]. 6.F.-K. Guo, C. Hanhart, G. Li, Ulf-G. Meißner, Q. Zhao, Phys. Rev. D 82, (2010); arXiv: [hep-ph]. 7.X.-H. Liu and Q. Zhao, Phys. Rev. D 81, (2010) 8.Y.J. Zhang, G. Li and Q. Zhao, Phys. Rev. Lett. 102, (2009); arXiv: [hep-ph]. 9.Y.-J. Zhang and Q. Zhao, Phys. Rev. D81, (2010) 10.Y.J. Zhang and Q. Zhao, Phys. Rev. D 81, (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, (2008) 14.Q. Zhao, G. Li and C.H. Chang, Phys. Lett. B 645, 173 (2007)

Thanks for your attention!

Anomalously large isospin violations: Theoretical interpretation: Wu, Liu, Zhao and Zou, arXiv: [hep-ph] Triangle singularitya0-f0 mixing

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