General Review of BES Physics, Achievement and Future Representing BES collaboration Weiguo Li IHEP, CAS 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 ( 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+p 2 )  z = 2.3 cm Dead time/event: 〈 10 ms

Korea (4) Korea University Seoul National University Chonbuk National University Gyeongsang Nat. Univ. Japan (5) Nikow University Tokyo Institute of Technology Miyazaki University KEK U. Tokyo USA (4) University of Hawaii University 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 China Shandong 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

(10 6 ) world largest J/  and  ’ data samples (10 6 ) J/ 

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 MC Data P P MC DATA MC DATA

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 SIMBES Data: 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 ) = (21.84  0.05  2.01)  Babar’s new result confirms our result.

Impacts on Physics Results (II) Angular Acceptance Impacts on PWA Results

Hight lights of BES Hight lights of BES Physics Results  Precise measurement of the mass of tau lepton  Precise measurement of R value in the energy range of 2-5 GeV  (2S) decays Study many decay modes and the 12% rule  J/  decays Light hadron spectroscopy, search for multi- quark candidates  (3770) decays and D physics

In 1992, BES made a scan over tau mass production threshold and measured the tau mass, BES M  = PDG M  = 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 GeV

Prediction of Higgs mass from standard model (95% C.L.)

Recent Physics Results J/  Decays Threshold enhancements in  pp and pK   in   +  - ;  in K*(892) 0 K +  - / 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 threshold Phys. Rev. Lett., 91 (2003) Mass: M=1859 MeV/c 2 Width:  < 30 MeV/c 2 (90% CL) J/    pp M(pp)-2m p (GeV) BG curve Eff. curve  2 /dof=56/56 Fitted peak Fitted curve  10  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/

Phase Space Data S-wave BW fit results M = (2075  12  5) MeV Γ = (90  35  9) MeV BR = (5.9  1.4  2.0)   2 /d.o.f = 31.1/26 About 7σ effect Phase space

Near K  threshold enhancement in J/  pK  Events/ 10 MeV NxNx NxNx NxNx PS, eff. corrected (Arbitrary normalization)

Its mass and width: (large uncertainty near threshold, high statistics is crucial!) Mass 1500~1650MeV Width 70~110MeV J P favors 1/2 - large BR(J/  pNx)Br(Nx  K  ) (  2*10 -4 ). What is it??Possibly N*(1535) with large coupling to K  K  molecular state ??

K*(892) K 0 *(1430), K 2 *(1430)K 1 (1270), K 1 (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) 0 K +  - κ

Accepted by PLB (hep-ex/ )

f 2 (1270) b 1 (1235) σ Spin 0Spin 2 No f 0 (1710)

σ f 2 (1270) b 1 (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) hep-ex/ submitted to PRL

M  in  (2S)  3   (770),  (2150) -- dominant BESII Preliminary ( PWA ) VP Mode (Con’t) 1.1  

Results on BRs ____________________________________________________________________________________________________________________________________________ BR BESII (10 – 5 ) PDG04 (10 – 5 ) Ψ(2S)   +  -   1.8   5 Ψ(2S)    5.1  0.7  0.8 < 8.3 Ψ(2S)   (2150)    +  -   2.5 ____________________________________________________________________________________________________________________________________________ # 1 st measurement or precision much improved # Interference taken into account BESII Preliminary ( PWA ) 1. VP Mode (Con’t) 1.1   (Con’t)

Test of pQCD 12% Rule BESII preliminary

D BF Measurements Semi-leptonic decays BF(D 0  K - e + e ) = (3.82  0.40  0.27)%, PDG (3.58  0.18)% BF(D 0  - e + e ) = (0.33  0.13  0.03)%, PDG (0.36  0.06)% Phys. Lett. B597(2004)39-46 preliminary BF(D +  K 0 e + e ) = (8.47  1.92  0.66)%, PDG (6.7  0.9)% = 1.15  0.29  0.09 PDG 1.4  0.2 Purely Leptonic decays, Three D +  + candidates,

D hadronic decay branching fraction by double tagging method 04

 (3770) production To 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 ! BES-II Preliminary ! Fitting results M  (3770) =  1.3 MeV PDG:  2.5 MeV  tot= 25.5  4.0 MeV PDG: 23.6  2.7 MeV  ee= 225  36 eV PDG: 260  40 eV  M(  (3770)-  (2S)) =86.8  1.3M eV PDG: 83.9  2.4 MeV

D Cross-section preliminary From D 0  K -  +, K -  +  +  - D +  K -  +  +  obs (DD)=6.14  0.12  0.50 nb  tree (DD)=7.88  0.15  0.74 nb Evidence for  (3770)  J/   +  - preliminary BF(  (3770)  J/   +  - )=(0.342   0.083)%  (  (3770)  J/   +  - )=(80  32  21)KeV

BEPCII/BESIII Project Two rings

BEPCII Design Goals

Physics Channel C. M. Energy (GeV) Peak Lumi. (10 33 cm -2 s -1 ) Cross Section (nb) Events per Year J/  ~  10 9  ~  10 6  ~  10 9 D ~5 25  10 6 DsDs ~  10 6 DsDs ~  10 6 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 f D, f Ds –D 0 –  D 0 mixing Check VDM, NRQCD, PQCD, study  puzzle

BEPCII/BESIII Physics Goals （ 2 ） Mechanism of hadron production ， low energy QCD ： precise R measurement  physics ： charged current ， m  and m  Search for new particles: 1 P 1 、  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

systemBES 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 = 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 with hundreds more statistics, with a better detector, should play an important roll in understanding the mesons and baryons.

Thanks

子系统 BES IIIBESII  XY (  m) = 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) = ps barrel 110 ps endcap 180 ps barrel 350 ps endcap  计数器 layers3 layers 磁场 1.0 tesla 0.4 tesla BESIII 和 BESII 比较

Trk. eff. -- Lamda Lamdabar CUTDataSIMBESSOBER Trk Rec.94.7%95.0%99.1% Good Trk94.6% 98.9% CUTDataSIMBESSOBER Trk Rec.94.4%94.2%99.3% Good Trk94.1%93.8%99.2% proton antiproton

Trk. eff. -- Lamda Lamdabar CUTDataSIMBESSOBER Trk Rec.88.8%88.6%93.0% Good Trk80.8%81.7%88.8% CUTDataSIMBESSOBER Trk Rec.90.0%90.2%94.0% Good Trk85.6%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 Θ μμ

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

Observed cross sections for DD-bar production at GeV Preliminary !

Tracking eff. of p, p from pp  +  - events MC Data MC Data P P