Overview of BES physics Yifang Wang Institute of High Energy Physics

BES experiments BESI Stared in late 80’s BESII Stared in late 90’s BESIII is starting now Data BESII J/  58 M ’’ 14 M  ’’ 33 pb -1 Continuum 6.4 pb -1 (  s=3.65 GeV) Performance  p/p 1.7%/  1+p 2  E/E 22% /  E PartID dE/dx+TOF Coverage 80% ~ 150 papers on PRL, PRD, PLB Rich physics at tau-charm BESII

R value and  excited states Significantly improved data quality in GeV region, From PDG Before BES After BES Before BES

An enhancement near the ppbar threshold J/    pp M(pp)-2m p (GeV/c 2 ) 00.2  Phys. Rev. Lett., 91 (2003) Observation of X(1835) Phys. Rev. Lett. Dec.31, 

Background Observation of a broad resonance in J/   K + K -  0 Phys. Rev. Lett. 97 (2006) PWA analysis and parity conservation considerations yield:  X pole position: Too many 1 --, Width is much broader than other mesons; multiquark state ?

Observation of N(2050) N*(1440)? N*(1520) N*(1535) N*(1650) N*(1675) N*(1680) ? Phys. Rev. Lett. 97 （ 2006 ） N(2050): 1/2 + 或 3/2 + N(1440):

Observation of an anomalous enhancement near the threshold of mass spectrum BES II 3-body phase space For a S-wave BW fit: M = 2075  12  5 MeV Γ = 90  35  9 MeV Phys. Rev. Lett. 93, (2004)

BEPC upgrade: BEPCII Unique physics opportunities In a regime of transition between pQCD and non- pQCD Can provide calibrations and tests of LQCD Rich spectra of light hadrons for Quark model test and for searches of new hadrons Rich gluonic matter production for QCD test Near the production threshold of tau-charm: good for quantum correlation constraints Complementary to LHC experiments

Physics at BEPCII/BESIII Precision measurement of CKM matrix elements Precision test of Standard Model Light hadron spectroscopy Charmonium physics Search for new physics/new particles Physics Channel Energy (GeV) Luminosity (10 33 cm –2 s –1 ) Events/year J/  ×10 10  ×10 7  ’ ×10 9 D* ×10 7 Ds ×10 6 Ds ×10 6 hep-ex/

Light hadron spectroscopy Baryon spectroscopy Charmonium spectroscopy Glueball searches Search for non-qqbar states J/  events is probably enough to pin down most of problems of light hadron spectroscopy Spectrum of glueballs from LQCD

Precision measurement of CKM ---- Branching rations of charm mesons V cd /V cs: Leptonic and semi-leptonic decays V cb: Hadronic decays V td /V ts: f D and f Ds from Leptonic decays V ub: Form factors of semi-leptonic decays Unitarity Test of CKM matrix CurrentBESIII V ub 25%5% V cd 7%1% V cs 16%1% V cb 5%3% V td 36%5% V ts 39%5%

Precision test of SM and Search for new Physics DDbar mixing DDbar mixing in SM ~ 10 – –10 DDbar mixing sensitive to “new physics” Our sensitivity : ~ Lepton universality CP violation Rare decays FCNC, Lepton no. violation 

BEPC II Storage ring: BEPC II Storage ring: Large angle, double- ring RF SR IP Beam energy: 1-2 GeV Luminosity: 1×10 33 cm -2 s -1 Optimum energy: 1.89 GeV Energy spread: 5.16 ×10 -4 No. of bunches: 93 Bunch length: 1.5 cm Total current: 0.91 A SR mode: 2.5 GeV

Commissioning milestones Oct , 2007: accumulation of electron/positron beams Nov. 18, 2007: first e+e- collision without BESIII detector Mar. 2008: Collision 500 mA × 500 mA, Lumi.: 1 ×10 32 cm -2 s -1 April 30,2008: Move BESIII to IP July 18, 2008: First event in BESIII

The BESIII Detector Be beam pipe SC magnet, 1T Magnet yoke MDC, 130  m CsI(Tl) calorimeter, 2.5 TOF, 90ps RPC

Japan (1) Tokyo University USA (6) Univ. of Hawaii, Univ. of Washington,Univ. of Minisolta, Carnegie Mellon Univ., RPI, Rochester Uni., China (23) IHEP, CCAST, Univ. of Sci. and Tech. of China Shandong Univ., Zhejiang Univ. Huazhong Normal Univ., Wuhan Univ. Zhengzhou Univ., Henan Normal Univ. Peking Univ., Tsinghua Univ., Zhongshan Univ.,Nankai Univ. Shanxi Univ., Sichuan Univ Hunan Univ., Liaoning Univ. Nanjing Univ., Nanjing Normal Univ. Guangxi Normal Univ., Guangxi Univ. Hong Univ., Hong Kong Chinese Univ. Europe (5) GSI, Germany University of Bochum, Germany University of Giessen, Germany JINR, Dubna, Russia Univ. of Torino, Italy

Drift chamber To measure the momentum of charged particles by its bended curvature in a magnetic field 7000 Signal wires: 25  m gold-plated tungsten Field wires: 110  m Al Gas: He + C 3 H 8 (60/40) Momentum Babar: ~ 110  m BELLE: ~ 130  m CLEO: ~ 110  m BESIII: ~ 130  m

BESIII CsI(Tl) crystal calorimeter To measure the energy of electromagnetic particles Barrel: 5280 crystals ， Endcap: 960 crystals Crystal: (5.2x 5.2 – 6.4 x 6.4) x 28cm 3 Readout: Photodiodes, 1cm  2cm, Energy range ： 20MeV – 2 GeV position resolution: 6 1GeV Tiled angle: theta ~ 1-3 o, phi ~ 1.5 o BELLE: CLEO: BESIII:

PID: TOF system Barrel: 2*88 BC408, 2.4 m long, 5cm thick Endcap ： 2* 48 BC 408 PMT: Hamamatzu R5942 探测器长 (cm) 本征分辨 BESIII ps CLEOII ps OBELIX ps BELLE25590~100 ps CDFII ps HARP ps

 system : RPC 9 layer, 2000 m 2 Special bakelite plate w/o lineseed oil 4cm strips, channels Noise less than 0.1 Hz/cm 2

First cosmic-ray event trigger+DAQ ＋ detector(MDC ＋ EMC ＋ TOF+MUON ） Trigger condition ： cosmic-rays

First collision event on July 19, M  ’ events collected in 2008

MDC calibration Reso. 128  m Eff.: ~ 98% σ P =12.0MeV/c=0.64% Reso.

dE/dx resolution dE/dx reso.: 5.80%  K p

TOF calibration TOF Barrel: 103 ps Design ： 100 ps Endcap TOF ： 125ps Design ： 110 ps

EMC calibration Barrel energy resolution energy deposit for e+e-   energy resolution for Bhabha events Position resolution for Bhabha 4.4 mm

Spatial resolution MUON Chamber Efficiency Single counting rate

Data Taking in 2009 March – April:  ’ – ~ 100 M events = 4*CLEOc = 7*BESII April- June: J/  –~ 500 M events = 8*BESII June ： a few days at 3.0 & 3.65 GeV After summer: –Possibly  ” scan if beam energy is stable and/or beam energy monitor is in place

Integral luminosity accumulated Corresponding to ~100M  ’ events

Peak luminosity in 2009

31 Physics at  ’ Spin-singlets –h c (resonance parameters, production & decays) –  c (resonance parameters, …) –  c ’ (resonance parameters, production & decays)  ’ hadronic decays –VP: , K*K, … (Dalitz analysis) –PP:  +  -, K + K -, K S K L (benefit from good momentum resolution and part ID)  c decays –New states

 ’ energy scan Beam energy spread: 1.4 MeV

Some physics signals 33  0 signal  (2S)   cJ  signal  signal

BESIII Software/Physics Workshop34  ’    l + l - : signals of  cJ,  0 and   00  c1  c2

Inclusive  Spectrum  c2  c1  co  c1,2   J/  cc

 confirm the X(1860) in J/  pp  confirm the X(1835) in J/  ’  +  -. check J/   ’  0  0 ?  confirm X(1810) in J/   confirm X(1580), X(2075), Y(2175) …  study inclusive photon spectrum  study J/ ,  ’,  ’  ’ and  0  0  provide  c sample (Br(J/     c )  1.3%)  more J/  and  c decay modes physics at J/ 

BESII data  58M J/  BESIII MC  58M J/  > 10   6  Confirm X(1835) at BESIII  5.1  > 10 

2 weeks data taking at BESIII 2 years data taking at BESII Confirm ppbar threshold enhancement at BESIII ( 58M J/  )

Y(2175) in J/  f0(980) at BESIII BESII data  58M J/  BESIII MC  58M J/    12 MeV 5.5    4 MeV > 10 

A lineshape scan of  (3770) L pb -1 PRL101 (2008) BES-II “fast energy calibration 45 d, ~ 90 pb energy points 9 energy points (may be a little bite more)

Summary physics program at tau-charm is very rich The BESIII detector is successfully constructed Computing facility and offline software are ready for large scale data production and physics analysis A total of 13 M psi’ events are collected in Detector calibration are performed, showing that –All detector components work well and stable –Detector resolution met design specifications A total of 100 M psi’ events are collected this year, and great physics results are expected to come soon