Decoding the riddle of Y(4260) and Zc(3900) Qiang Zhao Institute of High Energy Physics, CAS Decoding the riddle of Y(4260) and Zc(3900) Qiang Zhao Institute of High Energy Physics, CAS and Theoretical Physics Center for Science Facilities (TPCSF), CAS zhaoq@ihep.ac.cn Q. Wang, C. Hanhart, QZ, 1303.6355[hep-ph] The 9th International Workshop on Heavy Quarkonium, April 22-26, Beijing

Outline 1. Status of XYZ states – A jigsaw puzzle? 2. The nature of Y(4260) and Zc(3900) 3. Can we fit in some of the pieces of the jigsaw puzzle?

1. Status of XYZ states – A jigsaw puzzle?

S=0,1 c c L J=L+S 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

Close to DD* threshold 1010.5827[hep-ph] X(3872) X(3900) Close to DD* threshold Y(4260) Y(4360)

Observation of Y(4260) PRD77, 011105 (2008) Belle

[(5S) (1,2,3S) +–] >> [(4,3,2S) (1S) +–] (11020) 11.00 (10860) partial width (keV) – + 10.75 260 Zb (4S) 2M(B) 10.50 2 + (3S) Mass, GeV/c2 hb(2P) 10.25 430 1 b(2S) (2S) 10.00 hb(1P) 290 6 9.75 9.50 (1S) b(1S) Belle, Phys. Rev. Lett. 108 (2012) 122001

Belle, arXiv:1105.4583[hep-ex]; PRL108, 22001 (2012) Heavy quark symmetry breaking?

(5S)→B*B(*)π: Results Branching fractions of (10680) decays (including neutral modes): BBp < 0.60% (90%CL) BB*p = 4.25 ± 0.44 ± 0.69% B*B*p = 2.12 ± 0.29 ± 0.36% Assuming Zb decays are saturated by the already observed (nS)π, hb(mP)π and B(*)B* channels, one can calculate complete table of relative branching fractions: NEW! Belle PRELIMINARY B(*)B* channels dominate Zb decays ! A. Bondar at ICHEP2012

Resonant structure of (2S)00 Dalitz plot analysis with Zbs without NEW! Clear Zbs signals are seen in (2S)π0π0 Significance of Zb(10610) is 5.3σ (4.9σ with systematics) Zb(10650) is less significant (~2σ) Fit to the Zb(10610) mass gives M=10609±8±6 MeV M(Zb )=10607.2±2.0 MeV + Belle PRELIMINARY A. Bondar at ICHEP2012 10 10

It could be an opportunity for understanding the mysterious Y(4260). The mass of the charged charmonium-like structure Zc(3900) is about 3.899 GeV. It could be an opportunity for understanding the mysterious Y(4260). BESIII, arXiv:1303.5949 [hep-ex], talk by Z.Q. Liu

Belle, arXiv:1304.0121v1 [hep-ex], talk by C.P. Shen Xiao et al., arXiv:1304.3036v1 [hep-ex], see talk by K. Seth

Brief summary of the exp. progress New quarkonium-like states, i.e. X, Y, Z’s, are observed in experiment Do not fit in the conventional quarkonium spectrum as quark-antiquark states, e.g. X(3872), Y(4260), X(3900) etc. Most of these new states, such as X(3872), are located close to a two-particle threshold. Evidence for charged quarkonium states, e.g. Zb(10610), Zb(10650) and Zc(3900). In some cases, isospin or heavy quark symm. are violated. Good candidates for hadronic molecules or other non-standard configurations, e.g. tetraquarks, hybrids, etc.

3. The nature of Y(4260) and Zc(3900)

i) Charmonium production in ee    final particles Direct production of vector charmonium states Dynamics for charmonium interactions with final states Signals for exotics? Y(4260), X(3900) ? Any opportunities for understanding the vector charmonium spectrum? …… e+ * 1, / … … … e Belle, BaBar, and BESIII

Cross section lineshape in e+e- annihilations (3770), 1D X(3900) ? (4040), 3S e+e-  DD (4160) (4415) What is X(3900)? (see Wang et al., PRD84, 014007 (2011)) X(3900) has not been inlcuded in PDG2010 and PDG2012. Not in charmonium spectrum Why Y(4260) is not seen in open charm decays? … … (4260) Belle PRD77, 011103(2008).

Opportunities for a better understanding the nature of Y(4260) Theoretical prescriptions: Hybrid Tetraquark Glueball Hadronic molecules Calculations done by various approaches: Quark model Hadron interaction with effective potentials QCD sum rules Lattice QCD Cited 412 times! See 1010.5827[hep-ph] for a recent review.

It could be an opportunity for understanding the mysterious Y(4260). BESIII, arXiv:1303.5949 [hep-ex] The mass of the charged charmonium-like structure Zc(3900) is about 3.899 GeV. It could be an opportunity for understanding the mysterious Y(4260).

The signature of Y(4260) could be revealed by the associated Zc near the DD* threshold!  D(1868) D D0 Zc(3900), I,JP= 1, 1 D* J/   D M(Zc)  M(D) + M(D*) = 3.876 GeV

The implementation of Weinberg theorem is possible  The implementation of Weinberg theorem is possible S-wave dominates in the production of Zc(3900) S-wave dominates in DD* scattering to J/psi pi The Zc decays into hc pi is not necessarily suppressed by the NR power counting  Zc J/ Non-local pion radiation via triangle singularity kinematics: D1  D* D  J/ Q. Wang, C. Hanhart, QZ, 1303.6355[hep-ph]

Singularity kinematics in ee J/ D1    D* D  Zc J/ J/ Wang, Hanhart and Zhao, work to appear in arXiv.

“prediction” from a molecular Y(4260) in J/ decay, 1303 “prediction” from a molecular Y(4260) in J/ decay, 1303.6355[hep-ph] BESIII, 1303.5949[hep-ex]

Prediction for Y(4260)  hc  without  final state interactions The threshold phenomena explains the significant heavy quark spin symmetry breaking (see talk by C. Hanhart and talk by E. Eichten). Given the existence of a pole structure for Zc(3900), its production will be driven by the low-momentum DD* scattering apart from the cusp enhancement. This may also explain that its production is not favored in the B decays.

Singularity kinematics in ee (nS)  Two singularity regions by the BB* and B*B* thresholds can appear in the same c.m. energy in the (6S) decays. Two peaks are expected!

3. Can we fit in some of the pieces of the jigsaw puzzle?

Given that Y(4260) is dominantly a DD1 molecule, a cusp structure will unavoidably appear in the invariant mass of J/psi pi at the DD* threshold due to the presence of a two-cut condition. The cusp, however, seems to be insufficient to explain the relatively broad structure (~46 MeV). Thus, a charged charmonium with IG (JPC)=1 (1) is possible. Similar phenomena occur to the Upsilon(5S)  Zb pi and Zb’pi. Other implications of the molecular scenario are also made.

Thanks for your attention!

Quarkonium-like states near two-particle open threshold Weinberg (1963); Morgan et al. (1992); Baru, Hanhart et al. (2003), ...  Probability to find the hadronic molecule component in the physical state A

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

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

In case that the open threshold coupled channels play a role, typical ways to include such an effect are via hadron loops in hadronic transitions Q. Wang et al, PRD2012 X.-H. Liu et al, PRD81, 014017(2010); X. Liu et al, PRD81, 074006(2010) Y.J. Zhang et al, PRL(2009); X. Liu, B. Zhang, X.Q. Li, PLB(2009) Q. Wang et al. PRD(2012), PLB(2012) “ puzzle” G. Li and Q. Zhao, PRD(2011)074005 F.K. Guo and Ulf-G Meissner, PRL108(2012)112002 The mass shift in charmonium, E.Eichten et al., PRD17(1987)3090