Study of XYZ states at Xiao-Rui Lyu (吕晓睿) University of Chinese Academy of Sciences (UCAS), Beijing! （中国科学院大学，北京） (representing the BESIII collaboration) 1 Constitution of hadrons in QCD ordinary matter However, none of them are established and they are exotica!!! CCNU, Wuhan, Apr. 2014 2 Charmonium spectroscopy ❖ ❖ ❖ We observed all the charmonium states below DD threshold They fit quark potential model well However, still many missing states above DD threshold CCNU, Wuhan, Apr. 2014 3 Charmonium-like states above charm threshold Some of them are candidates of exotica!!! CCNU, Wuhan, Apr. 2014 4 Dataset in studying the XYZ states up to 2013 + ~0.5/[email protected], ~1.0/fb@4420GeV and other scan data in 2014 CCNU, Wuhan, Apr. 2014 5 What is the X(3872)? • Mass: Very close to D0D*0 threshold • Width: Very narrow, < 1.2 MeV • JPC=1++ [LHCb] • Production – in ppbar/pp collision – rate similar to charmonia – In B decays – KX similar to cc, K*X smaller than cc – e+e-à𝜸+X(3872) [BESIII, see next slides] • Decay rates: open charm ~50%, charmonium ~O(%) • Nature (very likely exotic) – Loosely D0D*0 bound state (like deuteron?)? – Mixture of excited 𝛘c1 and D0D*0 bound state? – Many other possibilities (if it is not 𝛘c1(2P), where is 𝛘c1(2P)?) CCNU, Wuhan, Apr. 2014 6 + -‐ Observation of e e à𝜸X(3872) PRL112, 092001 (2014) • Clear ISR 𝜓’ signal for data validation • X(3872) signal at around 4.23-4.26 GeV CCNU, Wuhan, Apr. 2014 7 + -‐ Observation of e e à𝜸X(3872) PRL112, 092001 (2014) CCNU, Wuhan, Apr. 2014 8 + -‐ Cross sections of e e à𝜸X(3872) PRL112, 092001 (2014) More statistics are desired. CCNU, Wuhan, Apr. 2014 9 Y states (vectors observed in Initial State Radiation) CCNU, Wuhan, Apr. 2014 10 Y states properties Y(4260), Y(4360) Properties: * not predicted in the quark model * tight upper limits on open charm decays Y(4260) Y(4360) arXiv:1010.5827 DD DD DD* DD* D*D* D*D* DDπ DD*π ΛcΛc BESIII will produce these stats directly in the annihilations. CCNU, Wuhan, Apr. 2014 11 + -‐ + -‐ Study of e e àπ π J/𝜓 at 4.26GeV PRL110, 252001 (2013) CCNU, Wuhan, Apr. 2014 12 + -‐ + -‐ Cross section of e e àπ π J/𝜓 PRL110, 252001 (2013) BESIII is measuring cross sections at more energy points, and more data is taken. CCNU, Wuhan, Apr. 2014 13 + -‐ + -‐ Measurement of e e àπ π h To understand the spin-‐alignment of the Y(4260) CCNU, Wuhan, Apr. 2014 c(1P) PRL111, 242001 (2013) 14 + -‐ + -‐ Observation of e e àπ π h c(1P) PRL111, 242001 (2013) CCNU, Wuhan, Apr. 2014 15 + -‐ + -‐ Cross sections of e e àπ π h c(1P) PRL111, 242001 (2013) CCNU, Wuhan, Apr. 2014 16 + -‐ + -‐ + -‐ Cross sections of e e àπ π hc(1P), π π J/𝜓 CPC38, 043001 (2014) • σ(e+e- àπ+π-hc(1P) ~ σ(π+π-J/𝜓); but lineshapes are different • σ(e+e- àπ+π-hc(1P): is it a combination of Y(4260) and Y(4360)? or something completely different? • Need more data to understand the shapes CCNU, Wuhan, Apr. 2014 17 Over populated Y states CCNU, Wuhan, Apr. 2014 18 Zc: charged charmonium-‐like states CCNU, Wuhan, Apr. 2014 19 + -‐ + -‐ e e àπ π J/𝜓 at 4.26GeV PRL110, 252001 (2013) CCNU, Wuhan, Apr. 2014 20 Zc+(3900) discovered at BESIII PRL110, 252001 (2013) Mass = (3899.0±3.6±4.9) MeV Width = (46±10±20) MeV 307±48events from APS/Alan Stonebraker 21 CCNU, Wuhan, Apr. 2014 Confirmations from other experiments Belle with ISR: PRL110, 252002 (2013) CLEOc data at 4.17 GeV: PLB 727, 366 (2013) 81±20events 6.1σ >5.2σ 159±49events Mass = (3894.5±6.6±4.5) MeV Width = (63±24±26) MeV Mass = (3885±5±1) MeV Width = (34±12±4) MeV Consistent results from other electron-‐positron annihilation experiments! CCNU, Wuhan, Apr. 2014 22 World attentions on the Zc(3900) CCNU, Wuhan, Apr. 2014 23 Nature of the exotic Zc+(3900) ➢ Its mass lies close to the threshold of m(D)+m(D*) DD* molecule? tetraquark? and ! other scenarios: • Cusp? • Threshold effect? • ... ➢ Other decay mode of the Zc(3900)? ➢ Partner(s) of the Zc? Evidence for neutral isospin partner! [T. Xiao et al., PLB 727, 366 (2013)] 24 CCNU, Wuhan, Apr. 2014 + e e àπ-Z+c(3885)àπ-(DD*)+ at 4.26GeV similar for the iso-‐spin partner mode PRL110, 252001 (2013) If Zc(3885) is Zc(3900): Angular distribution favors 1+ and disfavors 1-‐ or 0-‐ CCNU, Wuhan, Apr. 2014 25 + -‐ + -‐ Structures in e e àπ π h PRL111, 242001 (2013) c(1P) Reflection and possible Zc(3900) signal CCNU, Wuhan, Apr. 2014 26 + -‐ + -‐ Cross sections e e àπ Z PRL111, 242001 (2013) c(4020) Reflection and possible Zc(3900) signal No significant Zc(3900) signal is observed < 13 pb @4.23GeV < 11 pb @4.26GeV CCNU, Wuhan, Apr. 2014 27 + e e àπ-Z+c(4025)àπ-(D*D*)+ at 4.26GeV PRL113, 132001 (2014) 28 CCNU, Wuhan, Apr. 2014 Measurement of the + Z c(4025) assume it as a particle, Zc(4025), and fit to the π− recoil mass distribution resonance parameter: >10σ 401±47 Zc(4025) events Zc(4020)=Zc(4025)? Coupling to D*D* is much larger than to π-hc if they are the same state 29 CCNU, Wuhan, Apr. 2014 Zc family at BESIII Zc states CCNU, Wuhan, Apr. 2014 30 Zc family at BESIII arXiv:1303.5949 (138 citations) arXiv:308.2760 (53 citations) arXiv:1309.1896 (44 citations) arXiv:1310.1163 (22 citations) CCNU, Wuhan, Apr. 2014 31 Summary and perspectives • BESIII is taking leading role in studying of XYZ states • Observations of the four Zc states - what is the nature? new type of QCD state or dynamically generated structure • Connections among XYZ states - radiative transition e+e-à𝜸X(3872) from Y(4260)? - different line shapes between e+e- àπ+π-hc(1P) and e+e- àπ+π-J/𝜓 - hadronic transition between Y and Zc states? • In 2014, we take more (~2/fb) data at >4.3GeV • BESIII is now analyzing 2013 and 2014 data to explore these questions: - spin analysis, more decay modes, iso-spin parnters … • Many new results will come out soon. Stay tuned. CCNU, Wuhan, Apr. 2014 Thanks!! 谢 谢！ Especially to the staff of BEPCII and the computing center, the funding agencies, and all the friends of BES! 33
© Copyright 2024 ExpyDoc
