1. BESIII Status and Recent Results
Zhengguo ZHAO
(Representing BESIII Collaboration)
University of Science and Technology of China
NSTAR 2011, May 17-20, 2011, JLAB, USA

2. Outline Introduction Status Selected recent results
Excited baryon physics program
Summary

3. Beijing Electron Positron Collider (BEPC)
Ebeam: (2.3) GeV
sE: ×10-4
L: ×1033
Linac
BES
Storage ring

4. The BESIII Detector RPC Muon Counter Barrel: 9 layers SC magnet (1T)
Encaps: 8 layers
SC magnet (1T)
Magnet yoke
Time-of-flight(TOF)
sT(barrel): 90 ps
sT(endcap): 110 ps
Drift chamber
sp/p = 0.5% at 1 GeV
s(dE/dx)/dE/dx ~ 6%
ECAL calorimeter CsI(Tl)
sE /E ~2.5% at 1 GeV 4

5. BESIII Collaboration
~300 members from 48 institution of 9 counties
Europe (10)
Germany: Univ. of Bochum,
Univ. of Giessen, GSI
Univ. ofJohannes Gutenberg
Helmholtz Ins. In Mainz
Russia: JINR Dubna; BINP Novosibirsk
Italy: Univ. of Torino，Frascati Lab
Netherland：KVI/Univ. of Groningen
US (6)
Univ. of Hawaii
Univ. of Washington
Carnegie Mellon Univ. Univ. of Minnesota Univ. of Rochester
Univ. of Indiana
Korea (1)
Seoul Nat. Univ.
China(29)
IHEP, CCAST, Shandong Univ.,
Univ. of Sci. and Tech. of China
Zhejiang Univ., Huangshan Coll.
Huazhong Normal Univ., Wuhan Univ.
Zhengzhou Univ., Henan Normal Univ.
Peking Univ., Tsinghua Univ. ,
Zhongshan Univ.,Nankai Univ.
Shanxi Univ., Sichuan Univ
Hunan Univ., Liaoning Univ.
Nanjing Univ., Nanjing Normal Univ.
Guangxi Normal Univ., Guangxi Univ.
Suzhou Univ., Hangzhou Normal Univ.
Lanzhou Univ., Henan Sci. and Tech. Univ.
Hong Kong Univ., Hong Kong Chinese Univ.
Japan (1)
Tokyo Univ.
Pakistan (1)
Univ. of Punjab 5

6. Features of the BEPC Energy Region
Rich of resonances, charmonium and charmed mesons
Threshold characteristics (pairs of , D, Ds, charmed baryons…)
Transition between smooth and resonances, perturbative and non-perturbative QCD
Energy location of the gluonic matter and glueball, exotic states and hybrid
PDG 2010
The Y’s 6

7. Physics Topics at BES Light hadron spectroscopy
Search for exotic hadrons
Spectroscopy of meson and baryons
Charmonium
New charmonium states above open charm threshold.
Production and decay mechanisms
Spectroscopy
Open charm
Precision measurement of CKM matrix
Decay constants and form factor
D0-D0bar mixing, CPV
Precise measurement of R values,  mass, …
Search for rare decays, LVP, CP violation, etc.

8. BESIII Data Samples Previous BESIII (2009-2014) BESIII target J/
BESII: 58M
2009：225M
2012：1 B (?)
10B ’
CLEO: 28 M
2009：106M
2012：0.5B (?)
3 B
(3770)
CLEO：0.8 /fb
2010：0.9/fb
2011：2/fb
20 /fb
y(4010),
y(4160),…
& scan
CLEO: 0.6 /fb
2011: 0.5/fb (?)
2013：5/fb
R scan & Tau
BESII
2014

9. Results from BESIII Confirm BESII results
threshold enhancement in pp, X(1835), …
New improved measurements
hc, c, cJ, , …
New observations
cJ decays
hc decays
Light hadrons, …

10. pp Threshold Enhancement_
pp Threshold Enhancement _
Observed at BESII in 2003
Confirmed by CLEOc and BESIII
Agree with BESII results
BESII: J/pp
PRL 91 (2003) _
J/pp
BESIII preliminary
0.1
0.3
Mpp-2mp (GeV)
M= MeV/c2
G < 30 MeV/c2 (90% CL)
BESIII: (2S) J/
J/pp _
CLEOc: (2S) J/
J/pp
QWG2010
Z. Metreveli _
CPC 34, 421 (2010)
M= MeV/c2
G < 38 MeV/c2 (90% CL)

11. ’gpp _ No significant narrow strong enhancement near threshold
BESII
BESIII preliminary
PRL 99 (2007)
Mpp (GeV)
No significant narrow strong enhancement near threshold
(~2 if fitted with X(1860))
No significant narrow threshold enhancement _
Pure FSI interpretation of the narrow and strong pp threshold enhancement is disfavored. Other possibilities: conventional meson, pp bound state or glueball…..? _

12. Observation of X(1835) from J/ygp+p-h’
BESII: PRL95,262001(2005)
M=1833.7±6.1(stat)±2.7(syst)MeV
G=67.7±20.3(stst)±7.7(syst)MeV
X(1835) is confirmed at BESIII
Two new resonances are observed
PWA is needed, inference among the
resonances needs to be considered
h’->gr, p+p-h
State
M(MeV)
G(MeV)
Stat. sig.
(s)
X(1835)
1838.1±2.8
179.5±9.1 25
X(2120)
2124.8±5.6
101±14
7.2
X(2370)
2371.0±6.4
108±15
6.7
Total bkg
PRL 106 (2011)

13. Observation of X(1870) The f1(1285), (1405) and X(1870) primarily
Significance: 7.7 s
J/ywX, Xp+p-h
f1(1285)
h(1405)
X(1870)
BESIII preliminary
The f1(1285), (1405)
and X(1870) primarily
decay via a0(980)±
M=1873 ± 11 MeV
G=82 ± 19 MeV
Statistical error only!
Is X(1870) a new resonance, or h2(1870) or X(1835)?

14. a0(980) – f0(980) Mixing
Mixing intensity provides important information in understanding the nature of a0(980) and f0(980).
Narrow peak (8 MeV) at around 980 MeV can be expected in ηπ (J/ψ  f0  a0  ηπ case) or π+π- (c1  a0π0  f0π0  π+π-π0 case) invariant mass spectra.
J/ψ  f0  a0  ηπ
c1  a0π0  f0π0  π+π-π0

15. a0-f0 Mixing

16. a0-f0 Mixing

17. a0-f0 Mixing

18. Physics Program with Excited Baryon at BES
The understanding of the internal quark-gluon structure of baryons is one of the most important tasks in both particle and nuclear physics.
The systematic study of various baryon spectroscopy will provide us with critical insights into the nature of QCD in the confinement domain.
The available experimental information is still poor, especially for the excited baryon states with two strange quarks, e.g., *. Some phenomenological QCD-inspired models predict more than 30 such kinds of baryons, however only two are experimentally well settled. Totally only about 10% excited baryons are observed.

19. List of Nucleon Resonances (uud, udd)
PDG 2008
(**)
not well-established

20. Excited Baryons from Charmonium Decays
M (,, , , , K …) N
N (N, ,  …)
N*,*
JLab, ELSA, MAMI, ESRF,
Spring-8, ….
Excited baryons can be produced through J/ decays.
For J/  NN and NN decays, the N and N
are pure isospin ½ system.
Search for “missing” baryon states and hybrid
baryon with large data sample at BESIII/BEPCII.

21. N*(2050) from BESII ? PWA not yet done
Phys. Rev. Lett. 97 (2006)
N*(2065)
PWA not yet done

22. N*(2050) is also observed in
Phys. Rev. D 80, (2009)
M2(p0)
+ : data
hist.: PWA fit

23. N*(2050) stat. sig. >>5σ, the spin-parity favors 3/2+
M(MeV/c2)
(MeV/c2) JP
fraction(%)
Br (×10-4)
N(1440)
1/2+
9.74~25.93
1.33~3.54
N(1520)
3/2-
2.38~10.92
0.34~1.54
N(1535)
1/2-
6.83~15.58
0.92~2.10
N(1650)
1/2-
6.89~27.94
0.91~3.71
N(1710)
1/2+
4.17~30.10
0.54~3.86
N(2050)
3/2+
23.0~41.8
0.91~3.11
BESIII will provide better opportunity to study
of baryon spectroscopy!

24. N*(1535) from y’pph at BESIII_
N*(1535) from y’pph at BESIII
Yutie Liang’s talk for details ?
Preliminary

25. Preliminary Results from PWA
½- N(1535) is significant in the PWA
BESIII preliminary

26. Analysis of y’ppp0 at BESIII _
Preliminary
PWA is underway

27. Observation of χcJ decaying into ppK+K-_
Observation of χcJ decaying into ppK+K- _
COM mechanism can describe most of χcJ decays except χcJ→ΛΛ
So far, only ground states of baryon (p, Λ) pairs has been reported in χcJ decays.
Excited baryon state (Λ(1520)→pK) is observed for the first time in the χcJ decays at BESIII
χcJ→ Λ(1520) Λ(1520) _
χc0
χc1
χc2
BESIII

28. Observation of χcJ decaying into ppK+K-_
Observation of χcJ decaying into ppK+K-
Besides two-body component, three-body components χcJ→ pK+Λ(1520)+c.c. and χcJ→ppφ are also observed. _ _
cc0
cc1
cc2
< 1.00
B(ccJ->ppf) (10-5)
< 1.82 _ _ _ _
All are the first measurements from BESIII
Submitted to PRD. arXiv:

29. Summary Results are obtained from
BEPCII/BESIII upgrade completed successfully
Peak luminosity reached at 3770 MeV: 6.5x1032.
Data collected: 106 M (2S), 225 M J/ , 2.8 fb-1 at (3770).
~500 pb-1 data sample will be collected at 4.01 GeV by the end of May.
Higher statistics data will be accumulated in the
near future for J/, ’ data sample.
Results are obtained from
Baryon physics program is underway, stay tuned.

30. Upgraded BEPC-BEPCII Beam energy: 1.0 -2.3GeVRF SR IP
SC RF
RF Gallery
Linac tunnel
Beam energy: GeV
Luminosity: ×1033
Energy spread: 5.16 ×10-4
No. of bunches: 93

31. BES Data Samples Data sample at y(3770) CELO: ~900 pb-1
J/
(2S) 58 14 26
100
200
Data sample at y(3770)
CELO: ~900 pb-1
BESIII: 2.0 pb-1

32. BW fit yields: PWA is performed. Phys. Rev. Lett. 97 (2006) 062001
N*(2065)
BW fit yields:
PWA is performed.
well-established N*’s are fixed to PDG values.
for N*(2065), L=1 is much worse than L=0 in the fit.
 1/2+ or 3/2+ (improve log likelihood by 400)
1/2+ + 3/2+ (improve log likelihood further by 60)

33. Study of hc Inclusive analysis of (2S)  0hc
identify hc in the inclusive recoiling mass spectrum of 0.
E1-tagged analysis of (2S)  0hc, hc c
tag E1 photon (~503 MeV) in hc c
hc significance improved in inclusive 0 spectrum
Exclusive analysis of (2S)  0hc, hc c
hc hadronic decays

34. Observation of hc: Inclusive (2S)p0hc
Reconstruct hc from the recoil of inclusively identified p0
Fit: D-Gaussian signal + 4th Poly. bkg
background
subtracted 34

35. Observation of hc: E1-tagged (2S)0hc,hcghc
BESIII PRL 104, (2010)
background
subtracted
Recoil mass spectrum of identified
Tag photon from hc->ghc
First measurement
M(hc) = ± 0.13 ± 0.18 MeV/c2
(hc) = 0.73 ± 0.45 ± 0.28 MeV/c2 (< % CL)
Br(ψ(2S)π0hc )×Br(hcc ) = (4.58 ± 0.40 ± 0.50) ×10-4

36. Theory predicts much more baryons than what observed  missing baryons
baryon(qqq)
N(938)
From Q. Zhao

37. Agreement Between Data and MC + K
(MC)- (data) for pion- -

38. Study of cJ The cJ decays provide important information for
study gluonium: c → gg → (qq)(qq)
C. Amsler and F. E. Close,Phys. Rev. D 53, 295 (1996).
test of Color Octet Mechanism (COM)
G. T. Bodwin et al., Phys Rev. Lett. D51, 1125 (1995).
H.-W. Huang and K.-T. Chao, Phys. Rev. D54, 6850 (1996).
J. Bolz et al., Eur. Phys. J. C 2, 705 (1998).
First measurement of cJ   , c1  , 
First measurement of cJ   ……
(arXiv: , arXiv: , …)