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Qiang Zhao Institute of High Energy Physics, CAS

Institute of High Energy Physics, CAS. “Surprises” from charmonium decays. Qiang Zhao Institute of High Energy Physics, CAS and Theoretical Physics Center for Science Facilities (TPCSF), CAS zhaoq @ ihep.ac.cn. 2011 年 11 月 4 日， USTC ，合肥. Outline. 1. Some facts about quarks

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Qiang Zhao Institute of High Energy Physics, CAS

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  1. Institute of High Energy Physics, CAS “Surprises” from charmonium decays Qiang Zhao Institute of High Energy Physics, CAS and Theoretical Physics Center for Science Facilities (TPCSF), CAS zhaoq@ihep.ac.cn 2011年11月4日，USTC，合肥

  2. Outline 1. Some facts about quarks 2. Charmonium and charmonium-like states – resonance or non-resonance? 3. Direct evidence for open charm threshold effects in e+e- J/, J/0, and c 4. Puzzles in charmonium decays -- surprising or not? 5. Summary

  3. 1. Some facts about quarks

  4. pre-history of sub-atomic particles 1897: electron 1919: proton 1932: neutron 1933: positron 1935: pion predicted by Yukawa Thomson Rutherford Chadwick Joliet-Curie C.-Y. Chao Anderson From S. Olsen’s summer lecture in Beijing, 2010 p n p Yukawa

  5. Elementary particle “Zoo” in 1963 meson resonances baryon resonances “stable” hadrons X S L N K X* K* p m w Y* e “flavors” r Two “classes” of hadrons K2* “non-strange:” n, p, p, r, … D “strange:” L, S, K, K*, … From S. Olsen’s summer lecture in Beijing, 2010

  6. 1961: Gell-Mann, Nishijima & Nee’man: The Eightfold Way Quarks as building blocks of hadrons: meson (qq), baryon (qqq) Simple rules for quarks (Particle Data Group): 1) Quark has spin 1/2 and baryon number 1/3; 2) Quark has positive parity and antiquark has negative parity; 3) The flavor of a quark has the same sign as its charge.

  7. SU(3) multiplets of baryons made of u, d, and s SU(3) octet with JP=1/2+ S – (ssd) 0 (ssu) 2 Gell-Mann - Nishijima: Q=I3+Y/2=I3+(B+S)/2 333 =(3 6)  3 =(18)  (810) 1 + (suu) – (sdd) 0,  (sud) I3 –1 1 0 n (dud) p (uud)

  8. SU(3) multiplets of baryons made of u, d, and s S SU(3) decuplet 10 with JP=3/2+ –(sss) 3 Decuplet 10: –(sss) *– (ssd) *0 (ssu) 2 *– (sdd) 1 *+ (suu) *0 (sud) 3/2 3/2 1 1 I3 0 –(ddd) 0(udd) +(uud) ++(uuu)

  9. m3 Symmetric spin wavefunction: S=3/2 Symmetric flavor wavefunction: sss Symmetric spatial wavefunction: L=0 6/2 m1 r3 m2 2 A problem encountered: Violation of the Pauli principle and Fermi-Dirac statistics for the identical strange quark system? r1 r2 Jacobi coordinate • An additional degrees of freedom, Colour, is introduced. • Quark carries colour, while hadrons are colour neutral objects. 3  3  3 = (3  6)  3 = (1 8)  (8  10)

  10. Again: Are quarks real objects?

  11. Probe coloured quarks in electron-positron collisions e eq q e *  e * Hadrons q  e e Electron-Positron annihilations   êq2  (2/3)2  (1/3)2  (1/3)2  … R  uds …

  12. R   êq2 q : u(3/2) d(-1/3) s(-1/3) c(2/3) b(-1/3) t(2/3) R (2/3)2  (1/3)2  (1/3)2  [2/3] [2/3]  (2/3)2  [10/9] [10/9] (1/3)2  [11/9] [11/9]  (2/3)2  [15/9] But if quark carries color, one should have R  3 êq2

  13. R  3 êq2 q : u(3/2) d(-1/3) s(-1/3) c(2/3) b(-1/3) t(2/3) R 2 10/3 11/3 5 (2/3)2  (1/3)2  (1/3)2  [2/3] [2/3]  (2/3)2  [10/9] [10/9] (1/3)2  [11/9] [11/9]  (2/3)2  [15/9]

  14. 2/3 Particle Data Group 2010

  15. 1976 Nobel Prize: B. Richter and S. C.-C. Ting "for their pioneering work in the discovery of a heavy elementary particle of a new kind" Also seen in pNe+e-X y J R=2.2 >>2/3 10 J.J. Aubert et al., PRL 33, 1404 (1974) J.E. Augustine et al., PRL 33, 1406 (1974)

  16. Quarks are real building blocks of hadrons: meson (qq), baryon (qqq) • Quarks are not free due to QCD colour force (colour confinement). • Chiral symmetry spontaneous breaking gives masses to quarks. • Hadrons, with rich internal structures, are the smallest objects in Nature that cannot be separated to be further finer free particles. Convention (Particle Data Group): 1) Quark has spin 1/2 and baryon number 1/3; 2) Quark has positive parity and antiquark has negative parity; 3) The flavor of a quark has the same sign as its charge.

  17. Quantum Chromo-Dynamics: a highly successful theory for Strong Interactions Conventional hadrons Confinement Meson Baryon Asymp. freedom

  18. Remaining questions: • Why are the proper effective degrees of freedom for hadron internal structures? • What are the possible color-singlet hadrons apart from the simplest conventional mesons (qq) and baryons (qqq)? • What’s happening in between “perturbative” and “non-perturbative”? • … …

  19. Multi-faces of QCD: Exotic hadrons beyond conventional QM Hybrid Tetraquark Glueball Hadronic molecule Pentaquark The study of hadron structures and hadron spectroscopy should deepen our insights into the Nature of strong QCD.

  20. 2. Charmonium and charmonium-like states

  21. Charm quark and charmonium states Parity: P=(1)L+1 Charge conjugate: C=(1)L+S S=0 c c J/ L S=1 c c  L ……….

  22. Recent experimental progress 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.

  23. 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 S=0,1 c c L J=L+S

  24. 1010.5827 [hep-ph]

  25. Observation of X(3872) new Belle meas. <MX>= 3871.46 ± 0.19 MeV new CDF meas. MD0 + MD*0 3871.8±0.4 MeV dm = 0.35 ± 0.41 MeV • 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 • JPC = 2 is not ruled out

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

  27. Charged charmonium-like states S.K. Choi et al., PRL 100,142001 (2008) • Resonant structure Z(4430) • Close to D*D01 threshold • Q = 1, JP= 0,1,2 • M= 4433 MeV • = 45 MeV First direct evidence for an exotic quark configuration, i.e. (cc ud).

  28. arXiv:1105.4583[hep-ex]

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

  30. 1010.5827[hep-ph] X(3900) Close to DD* threshold

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

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

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

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

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

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

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

  38. 4. Puzzles in charmonium decays

  39. Puzzles in charmonium decays • “ 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, andhc0 • Could be more … … • Conjecture: • These puzzles could be related to non-pQCD mechanisms in charmonium decays due to intermediate D meson loops. • The intermediate meson loop transition could be a mechanism for the evasion of the helicity selection rule.

  40. Short-distance dominant – “12% rule” • pQCD expectation of the ratio between J/ and ' annihilation: g c c * JPC = 1 J/, ' J/, ' c* c* Large “12% rule” violation in  ! – “ puzzle” R() =  0.2 %

  41. (3770) non-DD decays g c • Contradictions in exp. observations: Non-DD (3770) c Up to 15 % BES-II: CLEO-c: < 9 % at 90% C.L. Updated results from CLEO-c : 1004.1358[hep-ex]

  42. Contradictions in pQCD calculations： • NRQCD leading order calculations gave negligible contributions from the (3770) non-DD decays. • Refs: Kuang and Yan, PRD41, 155 (1990); Ding, Qin and Chao, PRD44, 3562 (1991); Rosner, PRD64, 094002 (2001) • However, calculations including NLO yield significant corrections. • Ref: He, Fan and Chao, PRL101, 112001 (2008)

  43. Short-range pQCD transition; • Color-octet contributions are included; • 2S-1D state mixings are small; • NLO correction is the same order of magnitude as LO. • Results do not favor both CLEO and BES • NNLO ? pQCD calculation: BR(non-DD) < 5% Questions: 1) Would QCD perturbative expansion still be valid in the charmonium energy region? 2) Would other non-perturbative mechanisms play a role in (3770)  non-DD ?

  44. Recognition of possible long-range transition mechanisms • pQCD (non-relativistic QCD): • If the heavy cc are good constituent degrees of freedom, c and c annihilate at the origin of the (cc) wavefunction. Thus, NRQCD should be valid. • pQCD is dominant in (3770)  light hadrons via 3g exchange, hence the OZI rule will be respected. •  (3770) non-DD decay will be suppressed. • Non-pQCD: • Are the constituent cc good degrees of freedom for (3770)  light hadrons? Or is pQCD dominant at all? • If not, how the OZI rule is violated? • Could the OZI-rule violation led to sizeable (3770) non-DD decay? • How to quantify it?

  45. The (3686) and (3770) will experience or suffer the most from the DD open channel effects. Such effects behave differently in the kinematics below or above the threshold. (3770) D(cq) (3770) (ud) D (3770) non-DD decays c c Mass c c D D(qc) (du) (3770) DD thresh. (3686) (ud) D c c J/(3096) “ puzzle” D (du) (3686) JPC = 1 

  46. (3770) hadronic decays via intermediate D meson loops Quantitative study of (3770)  VP is possible. Y.-J. Zhang, G. Li and Q. Zhao, PRL102, 172001 (2009)

  47. The V  VP transition has only one single coupling of anti-symmetric tensor form Transition amplitude can thus be decomposed as: Long-range non-pQCD amp. Short-range pQCD amp.

  48. iii) Predictions for (3770)  VP. Could become sizeable, i.e. several percents, after add up a number different channels!

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

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

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