General Review of BES Physics,

Achievement and Future

Representing BES collaboration

Weiguo Li

IHEP, CAS

liwg@ihep.ac.cn

MENU 2004

Beijing, Aug. 30, 2004

• Introduction

• BES Physics Results

• BEPCII/BESIII Project

•Summary

BEPC consists of Linac 、 Storage Ring 、 Detector(BES ） and Synchrotron Facility(BSRF). Ground breaking in 1984 ， completed in 1988 within budget and according to the schedule. Soon after reached the designed performances.

BESII Detector BESII Detector ((1995-1997 upgraded1995-1997 upgraded))

VC: xy = 100 m TOF: T = 180 ps counter: r= 3 cm MDC: xy = 250 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

Korea (4)

Korea University Seoul National University

Chonbuk National UniversityGyeongsang Nat. Univ.

Japan (5)

Nikow UniversityTokyo Institute of Technology

Miyazaki UniversityKEK

U. Tokyo

USA (4)

University of HawaiiUniversity of Texas at Dallas

Colorado State University Stanford Linear Accelerator Center

UK (1)Queen Mary University

China (18)IHEP of CAS

Univ. of Sci. and Tech. of ChinaShandong Univ., Zhejiang Univ.

Huazhong Normal Univ. Shanghai Jiaotong Univ.

Peking Univ., CCAST Wuhan Univ., Nankai Univ.

Henan Normal Univ.Hunan Univ., Liaoning Univ.

Tsinghua Univ., Sichuan Univ. Guangxi Univ., Guangxi Normal Univ.

Jiangsu Normal Univ.

Data collected with BESI and BESII Ecm (GeV)

Physics BES Data Other Lab.

3.10 J/ 7.8106 8.6106

3.69 (2S) 3.9106 1.8106

4.03 1.0105 LEP

4.03 DS, D 22.3 pb-1 CLEO

3.55 m scan m 5 pb-1

2-5 R scan

2. 2.2,2.6,3.0

R value,

QED, (g-2)

QCD

6+85 points 2, MarkI Crystal Ball Pluto……

3.1 3.69 3.78

J/ (2S) (3770)

5.8107

1.46107

~27 pb-1

world largest J/ and ’ data samples (10(1066))

J/

0

10

20

30

40

50

60

MarkIII DM2 BESI BESII

01.11-02.399.11-01.3

0

2

4

6

8

10

12

14

MKI MKII MKIII CBAL BESI BESII CLEOc

BESII Detector Simulation

Understanding the detector simulation and Data/MC consistency are very important to the physics results,

BES simulation,

SOBER(BESI), detector gaussian response, no

hadron interaction (from MarkIII)

SIMBES(BESII), Geant3 based, better detector

responses

For example, the wire resolution is affected by the dE/dx of the MDC hits.

Example: Wire Resolution of MDC

dE/dx dependence Double Gaussian

Seems most difficult part!

Wire res. vs dE/dx (data)

Q OF HITS

Deviation

Important Variables To Be Checked

Main Drift Chamber

Reconstruction efficiency

Momentum resolution

Error matrix and chi2

dE/dx (PID efficiency)

TOF

TOF quality (efficiency)

Resolution &

PID efficiency for , K, p

Shower Counter

Reconstruction efficiency

Resolutions (E, z, phi)

Energy distributions for

e, mu and hadrons

Events used for Data/MC comparison

J/ e+e-, +-, pp, , ,

pp+-

(2S) J/ +- , etc.

Tracking eff. of from J/ events

Data/MC agrees well (for )

Histogram: MC

With error bar: Data

GeV/c

Tracking eff. of p, p from pp+- events

MCData

P

P

MCDATA

MCDATA

Error Matrix in +- channel SOBER SIMBES

TOF eff. of pion

TOF efficiency (pion) vs Momentum

GeV/c

Eff.

Energy in sc of p and p

SOBER SIMBESData: red, MC: black

Impacts on Physics Results (I)

BR(J/ +-0 ) from SIMBES is about 30%

higher than that from SOBER. It is also

about 30% higher than PDG.

Br(J/+-0) = (21.840.052.01)10-3

Babar’s new result confirms our result.

Impacts on Physics Results (II)

Angular Acceptance

Impacts on PWA Results KKJ /

Hight lights of BESHight lights of BES Physics Results

Precise measurement of the mass of tau lepton

Precise measurement of R value in the energy ran

ge of 2-5 GeV

(2S) decays

Study many decay modes and the 12% rule

J/ decays

Light hadron spectroscopy, search for multi-quar

k candidates

(3770) decays and D physics

In 1992, BES made a scan over tau mass production threshold and measured the tau mass,

BES +0.18+0.25M = 1776.96 -0.21-0.17

PDG +0.29M = 1776.99 -0.26

Corrected a mass shift of 7 MeV from previous measurements, proved that tau is one of the leptons.

R Measurement

• With an average error of 6.6%, compare with 15-20% errors from previous measurements • fine measurement of the structure at 3.7-4.5GeV

Prediction of Higgs mass from standard model

GeVm

GeVm

H

H

212

98 5838

GeVm

GeVm

H

H

170

62 5330

(95% C.L.)

Recent Physics Results

J/ Decays

Threshold enhancements in pp and pK

in +- ; in K*(892)0K+- / K+K- +-

Study of scalars in J/ decays

Many BF measurements

See SHEN, Xiaoyan’s talk for details

(2S) decays

12% Rule; (2S) ;

in (2S) J/ +-;

Many decay BF measurements of (2S) and CJ

(3770) decays

D BF measurements, (semi-leptonic, purely leptonic, hadronic decays)

DD cross-section;

(3770) resonance parameters from scanning

Anomalous enhancement of pp near thresholdPhys. Rev. Lett., 91 (2003) 022001

Mass: M=1859 MeV/c2

Width: < 30 MeV/c2 (90% CL)

J/pp

M(pp)-2mp (GeV)0 0.1 0.2 0.3

BG curve Eff. curve

2/dof=56/56

Fitted peak

Fitted curve +3 +510 25

BES II

Observation of an enhancement near p mass threshold in J/pK

process

The clear Λ signal in data shows high purity of signal.

Data/MC

Accepted by P. R. L., hep-ex/0405050

Phase Space

Data Data

pM pM

pK Kp

S-wave BW fit results

M = (2075 12 5) MeV

Γ = (90 35 9) MeV

BR = (5.9 1.4 2.0) 10-5

2/d.o.f = 31.1/26 About 7σ effect

Phase space

Near K threshold enhancement inJ/pK

)(GeV/c2KΛM

Eve

nts

/10

MeV

Nx

Nx

Nx

)(GeV/c2 MMM KKΛ

PS, eff. corrected

(Arbitrary normalization)

• Its mass and width:

(large uncertainty near threshold, high statistics is crucial!)Mass 1500~1650MeV

Width 70~110MeV

JP favors 1/2-

• large BR(J/pNx)Br(NxK) (2*10-4). What is it??

Possibly N*(1535) with large coupling to K K molecular state ??

K*(892)K0*(1430), K2*(1430) K1(1270), K1(1400)

ρ(770)

in J/K+K-+-

BES Preliminary

κ

K*0(1430)

K*(892)0 in J/K+K-+-

BES Preliminary

κ

in J/ K*(892)0K+-

κ

Accepted by PLB (hep-ex/0406038)

f2(1270)

b1(1235)

σ

Spin 0 Spin 2

No f0(1710)

σ

f2(1270)

b1(1235) BG

BRs for (2S)(,,)(,,’),K*K

measured

PWA for (2S)+ - 0

Background from continuum considered

using Ecm=3.65 GeV data sample

(2S) decays and 12% Rule

VP Modes

BESII Preliminary

VP Mode (Con’t)

Dalitz plot for J/ and (2S) 3 are very different

J/ Ψ 3 Ψ(2S) 3

PRD70 (2004) 012005

hep-ex/0408047 submitted to PRL

M in (2S) 3

(770), (2150) -- dominantBESII Preliminary ( PWA )

VP Mode (Con’t)

1.1

Results on BRs____________________________________________________________________________________________________________________________________________

BR BESII (10 – 5 ) PDG04 (10 – 5 )

Ψ(2S) + - 0 18.1 1.8 1.9 8 5

Ψ(2S) 5.1 0.7 0.8 < 8.3

Ψ(2S) (2150) + - 0 19.4 2.5____________________________________________________________________________________________________________________________________________

# 1st measurement or precision much improved

# Interference taken into account

BESII Preliminary ( PWA )

1. VP Mode (Con’t)

1.1 (Con’t)

2.111.2

Test of pQCD 12% Rule

BESII preliminary

D BF Measurements

Semi-leptonic decays

BF(D0 K-e+e) = (3.820.400.27)%, PDG (3.58 0.18)%

BF(D0 -e+e) = (0.330.130.03)%, PDG (0.36 0.06)%

Phys. Lett. B597(2004)39-46

preliminary

BF(D+K0e+e) = (8.471.920.66)%, PDG (6.7 0.9)%

= 1.15 0.290.09 PDG 1.4 0.2

Purely Leptonic decays,

Three D+ + candidates,

)(

)(0

0

e

e

eKD

eKD

MeV)365( 3212128113D

f

D hadronic decay branching fractionby double tagging method

04

(3770) productionTo get right resonance parameters, the two resonance productions and decays should be considered simultaneously. In this way the “correct” QED background ( ) can be determined correctly !

udsR

'

)3770(

BES-II Preliminary !

[GeV] cmE

obshad

0.142.24udsR

Fitting results

M(3770) =3772.51.3 MeV

PDG: 3769.92.5 MeV

tot= 25.5 4.0 MeV

PDG: 23.6 2.7 MeV

ee= 22536 eV

PDG: 260 40 eV

M((3770)- (2S)) =86.8 1.3M eV

PDG: 83.9 2.4 MeV

nb 99.011.9|MeV 8.3772)3770(

sprd

D Cross-section

preliminary

From D0K-+, K-+ + -

D+K- + +

obs(DD)=6.140.120.50 nb

tree(DD)=7.880.150.74 nb

Evidence for (3770)J/ +-

preliminary

BF( (3770)J/ +- )=(0.3420.142 0.083)%

( (3770)J/ +- )=(8032 21)KeV

BEPCII/BESIII Project

Two rings

BEPCIIBEPCII Design GoalsDesign Goals

Beam energy 1 – 2.1 GeV

Optimal energy 1.89 GeV

Luminosity 1 x 10 33 cm-2s-1 @ 1.89 GeV

Linac requirements Full energy injection: 1.55 1.89 GeV Positron injection rate > 50 mA/min

Dedicated SR 250 mA @ 2.5 GeV

Physics

Channel C. M. Energy

(GeV) Peak Lumi.

(1033cm-2s-1)

Cross Section

(nb)

Events per

Year

J/ 3.097 0.6 ~3400 10109

3.670 1.0 ~2.4 12106

3.686 1.0 ~640 3.0109

D 3.770 1.0 ~5 25106

Ds 4.030 0.6 ~0.32 1.0106

Ds 4.140 0.6 ~0.67 2.0106

Expected Number of Events in One Year’s Running

With such a data sample, a precise measurements are expected

BEPCII/BESIII Physic Goals

• Precise measurements of J/、 (2S) 、 (3770 ）Decays

• Precise measurement of CKM parameters

• Light quark hadron spectroscopy

• Excited baryon spectroscopy

• Other D and Ds physics: – precise measurement of D and Ds decays– measurement of fD, fDs – D0 –D0 mixing

• Check VDM, NRQCD, PQCD, study puzzle

BEPCII/BESIII Physics Goals （ 2 ）• Mechanism of hadron production ， low energ

y QCD ： precise R measurement• physics ： charged current ， m and m

• Search for new particles: 1P1 、 c ? 、 glueballs 、 quark-gluon hybrid 、 exotic states…

• Search for new phenomena: – rare decays;– lepton number violation; – CP violation in J/ and (2s) decays;

工工

BESIII Detector

system BES III

XY = 130 m

MDC P/P = 0.5 %(1 GeV)

dE/dx = 6-7 %

EMC E/√E = 2.5 %(1 GeV)

z,= 5-6mm (1 GeV)

TOF T = 90-100 ps Barrel

110 ps endcap

counter 9- 8 layers

Magnet 1.0 tesla

BESIII Main Parameters

BESIII Status• Design has been finished

• Most of the R&D work successful

• Detailed Budget and CPM available

• Most of the budget have been contracted

• Mass production has been started:– CsI Crystals– RPC muon chambers– Support structure and Yoke– Superconducting magnet– Drift chamber structure

BESIII Schedule

• 11/2004: supporting structure/yoke installation• 2-3/2005: endcap muon chamber installation• 5/2005: magnet installation• 10/2005: magnetic field mapping• 2/2006: EMC installation• 3/2006: MDC/TOF installation• 7/2006: BESIII debug and commissioning,

Cosmic ray• 10/2006: BESIII detector in beam-line• 11/2006: commissioning detector/machine

A few items are on critical path for BESIII

• Mechanical support and Yoke

• Mechanical support of Barrel EMC; Crystal

production

• Super-conducting Magnet

• Offline software

Technical Challenge

• Background issues

• PID, MDC, EMC performance;

• DAQ system

BESIII Collaboration

There are about 18 Chinese institutes in BES collaboration, about 10 are actively involved in BESIII project,

Physicists from US and Japan are participating in BESIII project,

More foreign participants are welcome.

Summary

BES has produced many interesting results, a good place to study light hadron spectroscopy, excited baryons, etc.

BEPCII/BESIII project will provide data wit

h hundreds more statistics, with a better dete

ctor, should play an important roll in underst

anding the mesons and baryons.

Thanks

子系统 BES III BESII

XY (m) = 130 250

MDC P/P (0/0) = 0.5 %(1 GeV)

2.4% (1 GeV)

dE/dx (0/0) = 6-7 % 8.5%

电磁量能器 E/√E(0/0) = 2.5 %(1 GeV)

z,(cm) = 0.6cm/√E

22% (1 GeV) 3 cm /√E

飞行时间 T (ps) = 90-100 ps barrel 110 ps endcap

180 ps barrel

350 ps endcap

计数器 9- 10 layers 3 layers

磁场 1.0 tesla 0.4 tesla

BESIII 和 BESII 比较

Trk. eff. -- Lamda Lamdabar

CUT Data SIMBES SOBER

Trk Rec. 94.7% 95.0% 99.1%

Good Trk 94.6% 94.6% 98.9%

CUT Data SIMBES SOBER

Trk Rec. 94.4% 94.2% 99.3%

Good Trk 94.1% 93.8% 99.2%

proton

antiproton

Trk. eff. -- Lamda Lamdabar

CUT Data SIMBES SOBER

Trk Rec. 88.8% 88.6% 93.0%

Good Trk 80.8% 81.7% 88.8%

CUT Data SIMBES SOBER

Trk Rec. 90.0% 90.2% 94.0%

Good Trk 85.6% 84.9% 90.5%

pion+

pion-

Good trk eff. (including hadron interaction

cross section) is fine in SIMBES.

Good trk. eff. has also been checked in e+e- and pipiJ/psi channels, all fine in SIMBES (NOT for SOBER)

See also Feng’s talk

Dimu channel Θμμ

Summary of SIMBES Checks

SIMBES is an ‘effective’ simulation of detector. Data/MC consistency has been greatly improved.

SIMBES has big impacts on physics results, not only on BRs. Many PDG results will be systematically renewed.

No big problems are observed in the systematic checks of SIMBES for the variables used in the physics analysis, although it is not perfect.

BESIII needs much more careful checks. Hope our experience may help the BESIII simulation.

R 值测量被国际粒子数据手册收录Physics Review D66(2002)261

nb 0.310.093.58 00 obs

DD

nb 0.260.082.56 obs

DD

nb 0.500.126.14 obsDD

Observed cross sections for DD-bar production at 3.773 GeV

KD0

KD0

KD

Preliminary !

Tracking eff. of p, p from pp+- events

MCData

MCData

P

P