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  this talk 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

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 theory at ccJ hadronic decays The e+e- machine provides LARGE CLEAN sample via y’gccJ Leading-order QCD Color octect theory

ccJ→VV (V=w, f) ccJ→ 00,  Are they small ?? 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 ×10-3 ff ww wf cc0 0.940.21 0.13 2.290.58 0.41 DOZI (Thy 0.45) cc2 1.700.30 0.25 1.770.470.36 DOZI (Thy 0.24) cc1 -- HSR DOZI HSR Ref: PLB630:7, 2005. PLB642:197,2006. PRD72,074001.Q.Zhao Are they small ??

BESIII @ BEPC II Beam energy: 1.0-2 .3GeV Design peak luminosity: 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

BESIII Data-taking Data samples: July 19, 2008: First e+e- collision event in BESIII Achieved: 0.32×1033 cm-2s-1 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’ 0.30

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

cc0,2→ 00,  / 0 → 

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 angle is the polar angle of  in 0 /  rest frame

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

y’ → ccJ, ccJ→00,  Unbinned maximum LH Fit (2S)00 Nc0 17443±167 Nc2 4516±80 (2S) Nc0 2132±60 Nc2 386±25 Unbinned maximum LH Fit Signal PDF determined from MC 2nd polynomial is used for bkg

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%)

Results Precision improved. Results are consistent with CLEOc. BR (10-3) c0 c2 00 BESIII 3.23±0.03±0.23±0.14 0.88±0.02±0.06±0.04 CLEO-c 2.94±0.07±0.32±0.15 0.68±0.03±0.07±0.04 PDG08 2. 43±0.20 0.71±0.08  3.44±0.10±0.24±0.13 0.65±0.04±0.05±0.03 3.18±0.13±0.31±0.16 0.51±0.05±0.05±0.03 2.4±0.4 <0.5 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.

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

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

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)

Observation of ccJff sideband

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

M(ff ) distribution Obtained from 106M y’ data BESIII Preliminary Obtained from 106M y’ data Contribution from non-resonance estimated from f sideband (as blue)

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

Observation of ccJ wf  0 

Distribution of M(wf) 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.

Summary of ccJ VV cc1 ff ww wf cc0 Observ. 1st Observ. DOZI cc2 HSR DOZI HSR We are finalizing this analysis.

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。