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

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

3. 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

4. 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, PLB642:197, PRD72, Q.Zhao
Are they small ??

5. BESIII @ BEPC II Beam energy: 1.0-2 .3GeV Design peak luminosity:RF SR RF
Beam energy:
GeV
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: July 19, 2008: First e+e-
collision event in BESIII
Achieved: ×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

7. EM transition inclusive photon spectrum
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; <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

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

11. y’ → ccJ, ccJ→00,  Unbinned maximum LH Fit (2S)00
Nc ±167
Nc2 4516±80
(2S)
Nc ±60
Nc ±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.
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.

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

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

21. Observation of ccJ wf  0 

22. 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.

23. Summary of ccJ VV cc1 ff ww wf cc0 Observ. 1st Observ. DOZI cc2 HSR
DOZI HSR
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。