1 overview of besii/besiii/bepc i current status ii recent results iii future plans iv summary...

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 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