1 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 University Tokyo Institute of Technology Miyazaki Univ. KEK USA (4) University of Hawaii University 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 China Shan 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 ~ 5  /cm 2  s at J/  peak, single bunch

Daily J/  operation of BEPC in Time (min) Beam Current (mA) I max:  50 mA,  beam  8-10 hrs Maximum hadronic event rate  8 Hz Injection time  min.

BEPC Beam Time Distribution HEPSRMachine Study Summer maintenance 5322 Unit: month

BESII Detector(upgraded from ) 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+p 2 )  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 GeV + 24 points separated beam operation + 7 points single beam operation for both e + and e -

R Values in 2-5 GeV  R/R(%) Priori BES: BES(total): 6.6 BES(common): 3.3

Values of R Below 10 GeV

The Impact of BES’s New R Values on the SM Fit 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 GeV agree well with our data

Relative Contributions to the Uncertainties of a  and  (M Z 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 GeV energy region

Ecm=2.2 GeV New generator LUARLW based on Lund Area Law

Thrust at 3.0 GeV Preliminary

A variable to test NLQCD, no data available for E cm < 10 GeV Preliminary

 (3770)  (2S) J/  Measurement of  (3770) Resonance Parameters Online fast analysis

World J/  and  (2S) Samples (/10 6 ) J/   (2S)

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 Decay PWA for 50 M BESII J/  events

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

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

Test of “15% Rule”

First Measurement Of B(  (2S)  +  - ) hep-ex/ B(  (2S)  +  - ) = 2.71  0.43  0.55 (BESI) Test of universality: B ee  B    B   /  B ll B ee B   B   /    1.1  1.4 Obtain  tot PDG:  ee = 2.12  0.18 keV  tot =  ee /B ll = 252  37 keV

Improve the parameters of  (2S) , B(h), B(  +  - ), B(  +  -J/  ) B(  +  -X) 24 energy points between 3.67 and 3.71 GeV Int. L = 760 nb -1

Future Plans Take data with BESII to M  (2S) - R in 2-3 GeV, large N had 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 cm -2 s 3.1GeV

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 I beam ~ 1A Low impendence vacuum pipe and kickers + upgrade: injector, power supply, monitor and control systems

SC magnet: T Drift chamber: He based gas, Al field wires, small cell TOF: 65 ps Double layer plastic Scintillator 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, 1 P 1,  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 f D, f Ds, 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 (M Z 2 ) and a  had, 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 100  BESII 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

Both Chinese Government agreed to support BEPC II. Intl. Review Meeting for feasibility study held in April 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 Status of BEPCII Project

Expected Event Rates/Year at BES III ParticleEnergy Single Ring （ 1.2f b -1 ） Double Ring (4f b -1 ) D0D0  ’’ 7.0   10 7 D+D+  ’’ 5.0   10 7 D+D+ 4.14GeV 2.0   10 7 +-+- 3.57GeV 3.67GeV 0.6     10 7 J/  1.6   10 9 ’’ 0.6   10 9

E cm (GeV)PhysicsBESI+BESIICLEOCBESIII 3.1 J/  7.8   mm 5 pb -1 >  (2S)3.9  pts scan 10 8 (?)  (3770) para Detailed scan  1  10 3 ? pb R scan6+85 pts (6.6%)2% (3-5GeV)3% Data collected with BES and expected from CLEOC and BESIII

Physics J/  D, D s  Entry 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 low  a 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 Limited for precision and high statistic experiments The short term future to 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 ~ /cm 2 ·s BESIII: DC+double layer TOF+L3 BGO+RPC/stream tube  counter  Expected commission time:

International Workshop for BESIII Date: Oct , 2001 Place: Beijing BESIII Physics Detector Design Collaboration You are welcome to participate the workshop in the most beautiful season in Beijing