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Charmonium Study at BESIII: Insights into Spin-Triplet States and Hadronic Decays

Discover the latest findings on charmonium states at BESIII, focusing on understanding P-wave spin-triplet states and light hadron spectroscopy. Explore the dynamics of charmonium decay and test QCD-based theories through e+e- collision data. Gain insights into the decay modes of ccJ and observe new channels for glueball searches. The BESIII experiment has demonstrated precision improvements and consistency with previous studies. Exciting results include the observation of ccJ decays to various final states, shedding light on the properties of charmonium states.

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Charmonium Study at BESIII: Insights into Spin-Triplet States and Hadronic Decays

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  1. Charmonium Results From BESIII 张景芝 高能物理研究所 2010.04.19 南昌高能物理会议

  2. Charmonium Study @BES • Spin singlet states are less known • hc see Bian J.M.’s talk • hc, hc(2S) not in this talk • P wave spin triplet states ccJ  this talk

  3. Leading-order QCD Color octect theory Why ccJ • Only a small part of decay modes are found (13% ,39%,26%) • To understand the P-wave charmonium decay dynamic, and light hadron spectroscopy. • Test QCD based theoryat ccJ hadronic decays • The e+e- machine provides LARGE CLEAN sample via y’gccJ

  4. ccJ→VV (V=w, f) • The past results • cc1VV are suppressed by Helicity Selection Rule (HSR) • cc1 ff, ww, S wave forbidden, only allowed for L=2. • ccJ fw OZI doubly suppressed. • ccJ→ 00,  • Interesting Channels for glueball searches Ref: PLB630:7, 2005. PLB642:197,2006. PRD72,074001.Q.Zhao Are they small ??

  5. BESIII @ BEPC II RF SR RF Beam energy: 1.0-2 .3GeV Design peak luminosity: 1×1033 cm-2s-1 (×100 BESII) Optimum energy: 1.89 GeV MDC: s(pT)/pT=0.32%0.37% at 1GeV s(dE/dx) = 5.8% TOF: 90 ps (for bhabha) EMC: s(E)/E=2.5% at 1GeV (22% at BESII) IP

  6. BESIII Data-taking Data samples: 106M y’ events (150pb-1 ) 42pb-1 at 3.65GeV 220M J/y events (65pb-1) y(3770) ~450 pb-1 Results presented are based on 106M y’ • July 19, 2008: First e+e- collision event in BESIII • Achieved:0.32×1033 cm-2s-1 0.30

  7. EM transition inclusive photon spectrum c2 c1 co c1,2 J/ c BESIII preliminary

  8. cc0,2→ 00, / 0 → 

  9. Event selection • No charged tracks • Photon: • Eg>50 MeV, timing • 0,  • -0.06<M()-m0<0.04; -0.09<M()-m<0.06 GeV/c2 • Decay angle cos < 0.95; • Events • Have two p0/h with a minimum c Decay angleis the polar angle of  in 0 /  rest frame

  10. Good agreement of data & MC M(gg) Number of g c(p0p0) ptr

  11. y’ → ccJ, ccJ→00,  (2S)00 Nc017443±167 Nc24516±80 (2S) Nc02132±60 Nc2386±25 Unbinned maximum LH Fit • Signal PDF determined from MC • 2nd polynomial is used for bkg

  12. Systematics • The systematic uncertainties from • g detection (1% per g) • p0(h) reconstruction (1% per p0) • Selection cuts • Signal/bkg shape, fit range • Trigger (0.1%) • Number of y’ (4%)

  13. Results • Precision improved. • Results are consistent with CLEOc. Note: the third error are due to the branching fractions of y’→ ccJ Published in Phys.Rev.D81:052005,2010.

  14. ccJV V Note: cc1 VV: S-wave forbidden; HSR suppression

  15. Event selection • Photons • |cosq|<0.93; Eg>25MeV • Charged tracks • |Vz|<5cm, |Vr |<0.5cm,|cosq|<0.8 • Events • Ncharged = 4; SQ=0; Ng>Nshould • Selection best g by minimizing 4C c2 . • f: |MKK – mf | <0.015 GeV; w: |Mppp0 – mw | <0.050 GeV • c2 <60

  16. E1 photon angular distribution • MC: E1 transition assumed in y(2S)gccJ dN/dcosqg ∝(1+acos2qg ) a = 1 (cc0) • -1/3 (cc1 ) • 1/13 (ccJ2)

  17. Observation of ccJff sideband

  18. ccJff (cont.) M(fKK) M(KK) M(KK) M(KK)

  19. M(ff ) distribution BESIII Preliminary • Obtained from 106M y’ data • Contribution from non-resonance estimated from f sideband (asblue)

  20. Observation of ccJ w(p+p-p0)w(p+p-p0) M(ppp) GeV Non-resonance & other backgrounds are investigated from w sideband. sideband (0.9-1.2) M(ppp) GeV M(ppp) GeV BESIII preliminary M(ww)GeV

  21. Observation of ccJwf  0 

  22. Distribution of M(wf) DOZI suppression BESIII preliminary ？ ？ M(wf) • Background studied from sideband & 100M MC. • Clear signal cc0w(p+p-p0)f(K+K-) seen.

  23. Summary of ccJVV • We are finalizing this analysis.

  24. 总结 • BESIII 从 2008开始取数据， 采集了106M y’ 和 220M J/y 样本。 • 验证MC模拟和实验数据相符。 • 利用110M y’，观测到了ccJff, ww, wf; 其中ccJwf 及 cc1ff, ww 是首次发现。 • BESIII 提高了 ccJ到双中性 赝标量介子对 分支比的测量，包括cc0,2p0p0， cc0,2hh. • 大量分析工作正在进行中，BESIII 预期更多新结果。

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