Charmonium results from BES

1. Charmonium results from BES Ronggang PING (For BES Collaboration ) International Workshop on e+e- collisions from Phi to Psi 13 - 16 October 2009, IHEP, Beijing

2. OUTLINE • Preliminary results from BESII • (2S)-+ • Measurement of  decay parameters • Search for CP violation in J/    • Preliminary results from BESIII • EM transitions • hc physics • cJ 00, • Observation of cJ  , ,  • Summary

3. Main building BEPCII BESIII

4. Preliminary results from BESII

5.  First observation of (2S)-+ Test of pQCD predictive power: gluon spin, quark distribution, and helicity conservation Except for (2S) -+ , (2S) BB(B=p,,-) observed by BESII and CLEOc Upper limit: <7.310-5 @90% C.L. CLEOc:PRD72,051108R(2005) This decay mode is thought to be mainly produced from the annihilation of three gluons into ss pair. M BESII preliminary M Nobs=4.51.8 Statistical significance ~ 5

6. Hyperon non-leptoinc decays play an important role for people to understand parity violation in particle physics  decay parameter  polarization

7. Helicity system • insufficient to observe CP violation in  decay

9. Events selected in 58M J/ data sample • statistical error dominant • insufficient to observe CP violation • more stringent upper bounds for d @ BESIII

10. Muon Counter TOF System Driftchamber CsI(Tl) Calorimeter Solenoid Mar. 6 – April 14, 2009 May 24 – June 2, 2009 100 M (2S) data 42 pb-1 data at 3.65 GeV Preliminary results from BESIII

11. Detector performance and calibration ●Layer 7 ●Layer 22 Wire reso. Design: 130 mm dE/dx reso.: 5.80% Design：6-8% CsI(Tl) energy reso. Design: 2.5%@ 1 GeV Barrel TOF reso.: 78 ps Design：80-90 ps Bhabha

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

13. PDG08 • hc status • Assign as JPC=1+- • not well established in experiment • width? Decay modes? • hc production • Can generated by pp colliding, but the cross-section is small with high background level. • Highly suppressed in e+e- collider via e+e-3*  hc • Production via (2S) decay (2S)  0hc.

14. challenges to search for hc • Small production branching ratio;ambiguous decay modes. CLEOc: ( PRL101,182003(2008) ) Br[(2S) hc]Br[hc ]=4.190.32 0.45)10-4 • It requires: • Large (2S) data sample • Good photon energy resolution. • High reconstruction efficiency for soft photon. • High luminosity of BEPCII and high quality of photon • detection of BESIII offer us opportunity to study hc

15. Observation of hc: E1-taggedy(2S)p0hc,hcghc N(hc)= 2540±261 c2/d.o.f = 39.5/41.0 background subtracted BESIII preliminary BESIII preliminary • Select inclusive p0 • Select E1-photon to tag hc • A fit of BWRes. signal+ sideband bkg. yield: M(hc)Inc = 3525.16±0.16MeV G(hc)Inc = 0.89±0.57MeV (First measurement) Br(y’p0hc)×Br(hcghc)Inc =(4.69±0.48(stat)) ×10-4 (G(hc) floated) =(4.69±0.29(stat)) ×10-4 (G(hc) fixed at G(cc1))

16. Observation of hc : Inclusive y(2S)p0hc BESIII preliminary BESIII preliminary Inclusive p0 recoil mass spectrum background subtracted • Select inclusive p0 • A fit of D-Gaussian signal + 4th Poly. bkg yield N(hc) = 9233±935, c2/d.o.f = 38.8/38.0 • Combined inclusive and E1-photon-tagged spectrum Br(y’p0hc) = (8.42±1.29(stat)) ×10-4 (First measurement) Br(hcghc) = (55.7±6.3(stat)) % (First measurement) 16

17. Systematic errors Sources Background shape, fit range, width of bin Absolute energy calibration Instrument resolution shape E1 photon efficiency p0 efficiency Number of charged track Number of p0 Veto XJpsi N(y(2S)) Mass of y(2S)(in the calculation of recoiling mass) Modeling of signal shape Systematic errors under study

18. Summary ofhc measurement M(hc)Inc= 3525.16±0.16 (stat.) MeV (3525.28±0.19±0.12 MeV PRL101,182003(2008),CLEOc) (hc)Inc= 0.89±0.57 (stat.) MeV (First measurement) Br((2S) 0hc) =(8.42±1.29 (stat.) ) ×10-4 (First measurement) Br((2S) 0hc)×Br(hcc)Inc =(4.69±0.48 (stat.) ) ×10-4 ((4.22±0.44±0.52) ×10-4 inc (4.16±0.30±0.37) ×10-4 avg ) Br(hcc) =(55.7±6.3 (stat.) )% (First measurement) • BESIII preliminary results are consistent with CLEOc measurements • Precision improved • First measurements: (hc), Br[(2S)0hc], Br(hc c)

19. Study of (2S)→ 00 , ( → ,0 → ) (2S)00 Nc016645±175 Nc24149±82 (2S) Nc01541±56 Nc2291±23 • Interesting channels for glueball searches • Based on 100M y(2S) • BK study from 100M inclusive MC sample and 42pb-1 continuum sample • Unbinned Maximum Likelihood fit: • Signal: PDF from MC signal • Background: 2nd order Poly. CLEO-c arxiv:0811.0586

20. Observation of ccJ ff, ww,fw • Test QCD-based theory at ccJ decays • Puzzles for cc0  VV: no helicity suppress • cc1 ff, ww is only allowed for L=2, suppressed ? • cc1 fw OZI doubly suppressed • surprisingly these decays observed at BESIII Eur.Phys.J.C2.705; Eur.Phys.J.C14,643 PLB 642,197(2006) PLB 630,7 (2005)

22. + : data Histogram: MC + : data Histogram: MC

23.  signals are clearly observed in cJ  K+K- • backgrounds are very lower

24. Two  sideband • c1   signals are clearly observed • backgrounds and non-resonance contributions are very lower • Branching fraction measurements are ongoing

25. Data m+ - 0 (GeV) • c1    signals are clearly observed • backgrounds and non-resonance contributions are studied with two- sidebands, very lower • Branching fraction measurements are ongoing

26.   0 mKK versus m for Data mK+K- (GeV)

27. c0   signals are clearly observed • backgrounds and non-resonance contributions are studied with  and  sidebands, very lower • Branching fraction measurements are ongoing

28. Summary • (2S)-+ observed at BESII •  decay parameter and  EMD studied in J/   at BESII • hc signals observed in BESIII 100 M (2S) data sample. • resonance parameters: • Br( (2S) 0hc) • Br(hc ) • c1  , ,  observed branching fraction measurement ongoing • BESIII detector performance excellent and work well Thanks for your attention!

29. Backup slides

30. BESIII Commissioning and data taking milestones Mar. 2008: first full cosmic-ray event April 30, 2008: Move the BESIII to IP July 19, 2008: First e+e- collision event in BESIII Nov. 2008: ~ 14M y(2S) events collected April 14, 2009 ~110M y(2S) events collected May 30, 2009 42 pb-1 at continuum collected July 28, 2009 ~200M J/y events collected Peak Lumi. @ Nov. 2008: 1.2 1032cm-2s-1 Peak Lumi. @ May 2009: 3.21032cm-2s-1

31. BEPC II Storage ring: Large angle, double-ring RF SR RF Beam energy: 1.0-2 .3GeV Luminosity: 1×1033 cm-2s-1 Optimum energy: 1.89 GeV Energy spread: 5.16 ×10-4 No. of bunches: 93 Bunch length: 1.5 cm Total current: 0.91 A BESIII detector IP

32. Endcap Eg Barrel Eg Endcap(0.84<|cosq|<0.92): E > 50MeV Barrel(|cosq|<0.8): E > 25MeV dq Good photon selection Angle between neutral track and the nearest charged trackdq<20 Time window for the EMC signals

33. Event selection – for hcghc • p0selection • Photon polar angle: |cosq|<0.8 • Photon energy: E>40MeV • Each photon belongs to only one p0 • Mgg∈[0.12,0.145]GeV/c2 • Perform 1C kinematic fit for each p0 candidate • (no c2 requirement) • E1-photon tagging in hcghc • 450MeV<Eg<540MeV • Veto p0 (0.100-0.145GeV/c2) • Veto h (0.530-0.560GeV/c2) If the invariant mass of the E1 photon and any other photon in the event iscompatible with either ap0 or a h, the E1 photon candidate is rejected.

34. Distributions of p0 candidate and pp recoiling mass c2of 1C Ehigh Elow Mgg Events p+p-recoil mass p0p0recoil mass DATA/MC agree well

35. BESIII preliminary results are consistent with CLEOc • measurements • Precision is improved • First measurements: (hc), Br[y(2S)p0hc], Br(hcghc)