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Charmonium Results From BESIII

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. Charmonium Study @BES. Spin singlet states are less known h c  see Bian J.M.’s talk h c , h c (2S) not in this talk P wave spin triplet states c cJ  this talk. Leading-order QCD. Color octect theory. Why c cJ.

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Charmonium Results From BESIII

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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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