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Overview of BESII/BESIII/BEPC
I Current Status
II Recent Results
III Future Plans
IV Summary
Zhengguo ZHAO Dept. of Phys., UM, USA
(and IHEP of CAS, Beijing)
Electron-Positron Collider from to Z, Snowmass2001, USA
Korea (3)
Korea Univ. Seoul National Univ.
Chonbuk National Univ.
Japan (4)
Nikow UniversityTokyo Institute of Technology
Miyazaki Univ.KEK
USA (4)
University of HawaiiUniversity of Texas at Dallas
Colorado State University Stanford Liner Accelerator Center
UK (1)Queen Mary Univ.
China (15)IHEP of CAS, CCAST
Univ. of Sci. and Tech. of ChinaShan Dong Univ. , Nan Kai Univ.
Peiking Univ., Shanghai Jiaotong Univ. Zhe Jiang Univ., Wu Han Univ.
Hua Zhong Normal Univ. Henan Normal Univ.,
Hunan Univ., Liaoning Univ. Tsinghua Univ.Sichuan Univ.
The BES Collaboration
The Beijing Electron Positron Collider
A unique e+e- machine operating in 2-5 GeV since 1989
L ~ 51030 /cm2s at J/ peak, single bunch
Daily J/ operation of BEPC in 2000-2001
Time (min)
0
10
20
30
40
50
60
0 500 1000 1500
Bea
m C
urr
ent
(mA
)
Imax: 50 mA, beam 8-10 hrsMaximum hadronic event rate 8 HzInjection time 15-20 min.
BEPC Beam Time Distribution
HEP SR Machine
Study
Summer maintenance
5 3 2 2
Unit: month
BESII Detector(upgraded from 1995-1997)
VC: xy = 100 m TOF: T = 180 ps counter: r= 3 cm MDC: xy = 200 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.4 % = 7.9 mr B field: 0.4 T p/p=1.8%(1+p2) z = 2.3 cm Dead time/event: 10 ms
BESII J/ Data Taking History(20/11/1999-7/04/2001)
400K
300K
Status of BEPC and BESII
• Both machine and detector are benefiting from the upgrade
• BESII
seriously suffering aging problem
- electronics, BSC, muon identifier and some other
parts are more than 12 years old
- not good enough E/E, p/p and PID
- endcap detector information is not good enough
for physics analysis
Recent Results from BES
• R Scan in 2-5 GeV
• Charmonium physics
- Results from J/ data
- Results from (2S) data
BES R Scan in 2-5 GeV
March-May, 1998: • 6 energy points at 2.6, 3.2, 3.4, 3.55, 4.6, 5.0 GeV
single and separated beam operation at all points
Feb.- June, 1999:• 85 energy points at 2.0-4.8 GeV
+ 24 points separated beam operation
+ 7 points single beam operation for both e+ and e-
R Values in 2-5 GeV
37704040
4160 4415 R/R(%)Priori BES: 15-20
BES(total): 6.6BES(common): 3.3
Values of R Below 10 GeV
The Impact of BES’s New R Values on the SM Fit
68 90
210170
090.0890.128)( 12 ZM
046.0936.128)( 12 ZM
1995 before BES R data
2001 after BES R data
Experimental R-value Below 5 GeV and QCD Calculation
QCD calculation (M. Davier et al.) in 2-3.6 GeV agree well with our data
Relative Contributions to the Uncertainties of a and (MZ
2)
Before BESII R
After BESII R
CLEOC and BESIII
CLEO
CMD2, KROE
PEPN
Other Topics With R Scan Data
• Pion form factor measurement
• Measurement of (e+e-p p-bar)
• Events shape of the hadronic events
• Measurement of the (3770) resonance parameters
• Structures in 3.7-4.5 GeV energy region
Ecm=2.2 GeV
New generator LUARLW based on Lund Area Law
)( ppee Thrust at 3.0 GeVPreliminary
)/ln( beamppA variable to test NLQCD, no data available for Ecm < 10 GeV
Preliminary
(3770)
(2S)J/
Measurement of (3770) Resonance ParametersOnline fast analysis
World J/ and (2S) Samples (/106)
J/ (2S)
05101520253035404550
MarkIII DM2 BESI BESII0
0.5
1
1.5
2
2.5
3
3.5
4
MARKI MarkII MarkIII CrystalBall
BESI
Preliminary Results from Charmonium Decays
With J/ data sample, BES has been
• Searching for glueball, hybrid and exotic states
• Studying of light hadron spectroscopy and excited baryonic states
• Searching for LFV and rare decays
Recent preliminary results
• Study of the structure around 1.7 GeV mass region
• PWA analysis of J/+-, K+K-, +-, K+K-…
• Search for Chiral partner from J/+-
• Study of excited baryonic states (N*, *…)
F.A. Harris EPS01
J/ Radiative Decay
PWA for 50 M BESII J/ events
J/ Hadronic DecayPWA for 50 M BESII J/ events
J/ Hadronic Decay
J/ Hadronic Decay
Study of Excited Baryonic States From J/ Hadronic Decay
• Probe internal structure of light quark baryons
• Better understand the strong force in perturbative region; better determine masses and widths of poorly known states
• Search for missing baryons predicted by the Quark Model
Advantage:
• Pure isospin ½ N, N• Large branching ratio ~10-3
npJ /
24 M
J/pK
(2S) Physics (only BESI data)
(2S) is an important laboratory to study
- charmonium family members
- non-relativistic perturbative QCD
e.g. test of “15% rule” from non-relativistic perturbative QCD
BES has measured many decay channels - many for the first
time, many filled up the PDG and improve the precision
%15]/[
])2([
]/[
])2([
eeJB
eeSB
hdronJB
hdronSB
Test of “15% Rule”
First Measurement Of B((2S)+-)hep-ex/0010072
• B((2S)+-) = 2.710.43 0.55 (BESI)
• Test of universality:
Bee B B /0.3885 Bll
Bee B B /0.3885
8.8 1.3 10.3 3.5 7.0 1.1 1.4
• Obtain tot
PDG: ee= 2.12 0.18 keV
tot = ee/Bll = 252 37 keV
Improve the parameters of (2S)
, B(h), B(+ -), B(+-J/)B(+-X)
24 energy points between 3.67 and 3.71 GeVInt. L = 760 nb-1
Future Plans
• Take data with BESII to 2003 - 16 M (2S)
- R in 2-3 GeV, large Nhad in 2-3 GeV - (3770)?
• BESIII at BEPCII is the future of the BES Double rings with large angle crossing in BEPC tunnel. Expect Lumi. 1033 cm-2s-1
@ 3.1GeV
e-
RFRF SR
e+
IP
Double Ring Scheme in BEPC tunnel
Design Goals and Main Parameters
Key Technology for BEPCII
• 500 MHz SC RF system• SC Micro- quads • Large angle cross: 11 mrad.• 93 bunch / ring with Ibeam~ 1A
• Low impendence vacuum pipe and kickers
+ upgrade: injector, power supply, monitor and control
systems
SC magnet: 1-1.2 T
Drift chamber: He based gas, Al field wires, small cell
TOF: 65 psDouble layer plasticScintillator
Electromagnetic calorimeter: L3 BGO
identifier: RPC or stream tubes
Physics Features in BEPC Energy Region
• Rich of resonances, charmonium and charmed mesons
• Threshold characteristics• Transition between smooth and resonances, perturbative and non-perturbative QCD
• Energy location of the gluonic matter and glueball, exotic states and hybrid
Physics Program
• Meson spectroscopy with J/, (2S) data
qqbar, excited baryonic states (N*, *, *, *... ), hybrid, glueball, 1P1, c
’
Best laboratory to elucidate a tricky situation; unique opportunity for QCD studies and new level of understanding
• Interactions with charmed mesons
Absolute Br, decay constants fD, fDs, CKM elements (c), charmed baryons
Unique opportunities, results needed for advances in other area, e.g. b physics, thus complementary
• New study of the lepton
- lower limit on mass;
- determination of m 0.1 MeV(needed in the future to test lepton universality - study of weak current - extend QCD studies
• Precision R scan [at ~(1-3)% level)]
- Input for had(MZ2) and ahad, very important for testing
of SM and hunting for new physics beyond the SM - Unique test of QCD (hadron production mechanism, e.g. e+e- V, T, Baryon pairs
A real challenge experiment; may needs 100BESII R data and good detector
Physics Program
• New physics
- mixing
- CP violation in , J/, (2S) decays
- Lepton flavor violating processes
e.g. J/’, =e, , - Rare decay (e.g. J/DX, Non-SM decay)
Taking advantage of threshold production and much
high statistics.
Physics Program
00DD
• Both Chinese Government agreed to support BEPC II.• Intl. Review Meeting for feasibility study held in April 2-
6. Both options are supported, double ring option is preferred.
• Double ring option is supported by CAS. Proposal will be submitted in July. Budget ~ 75 M US$ from government, 5 M $ expected from International collaboration.
• Detector design has not been finalized.
• R&D work started.
• Expect to start running in 2005-2006
Status of BEPCII Project
Expected Event Rates/Year at BES III
Particle Energy Single Ring ( 1.2fb
-
1 )
Double Ring (4fb
-1)
D0 ’’ 7.0106 2.3107
D+ ’’ 5.0106 1.7107
D+ 4.14GeV 2.0106 0.72107
+- 3.57GeV3.67GeV
0.6106
2.9106
0.2107
0.96107
J/ 1.6109 6109
’ 0.6109 2109
Ecm(GeV) Physics BESI+BESII CLEOC BESIII
3.1 J/ 7.8 106
5 107
109 1010
3.55 m 5 pb-1 >106
3.69 (2S) 3.9 106
24 pts scan
108(?) 109
3.77 (3770)
paraDetailed scan 107 108
4.03 1 103 ?
4.14 22.3 pb-1 106 107
4.6 105
2-5 R scan 6+85 pts (6.6%) 2% (3-5GeV) 3%
Data collected with BES and expected from CLEOC and BESIII
0*0DD
ss DD
cc
Physics J/ D, Ds
Entry 61 46 7 2
BES Entries in PDG 2000
Total 116 entries. 78 since 1997
Comments to CLEOC & BEPCII• Physics in tau-charm energy region is sill very rich in the
B’s era: Many needs to be improved, many needs to be searched and some are expected to be discovered. BESII/BEPC is limited by both statistical and systematic uncertainties for the important mission.
• CLEOC: Excellent detector is already there; machine has no problem to shift to a charm factory; cost is lowa wise choice.
• BESIII: The only HEP lab. in China; 10 years experiences in tau-charm physics, high lumi of BEPCII natural extension and very competitive.
• Both CLEOC and BESIII are needed. Both will be the eminent players and contributors to the physics in tau-charm energy region in the world in the near future
Any interesting and important physics result from single experiment is difficult to be accepted. Independent check and confirmation are needed. (A+D+L+O at LEP, CLEO, Babar+Belle for B physics, CMS+ATLAS at LHC)
Summary• BESII/BEPC: - Benefit from the upgrade finished in 1997 - Limited for precision and high statistic experiments
• The short term future to 2003 - accumulate 16 M (2S) events - possibly scan R below 3 GeV or collect 40 nb-1 at (3770)
• BES is still producing interesting physics results from BESI and BESII data – R and charmonium decay
• The future of the BES will be the BEPCII/BESIII
BEPCII: L ~ 1033 /cm2·s
BESIII: DC+double layer TOF+L3 BGO+RPC/stream tube counter
Expected commission time: 2005-2006.
International Workshop for BESIII
Date: Oct. 12-13, 2001
Place: Beijing
• BESIII Physics
• Detector Design
• Collaboration
You are welcome to participate the workshop in the most beautiful season in Beijing
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