1. 1 BEPCII/BESIII Frederick A. Harris University of Hawaii QWG Meeting Sept. 20-22, 2003 Fermilab Representing:

2. 2 The Beijing Electron Positron Collider L ~ ~5  10 30 /cm 2  s at J/  peak E cm ~2-5 GeV A unique e + e - machine in the  -charm energy region since 1989.

3. 3 On Feb. 10, 2003, the Chinese government, the state council, approved officially the BEPCII/BESIII upgrade project

4. 4 BEPC II Storage ring: BEPC II Storage ring: Large angle, double-ring e - RF SR e + IP

5. 5 BEPCII Design goal

6. 6 Passed SLAC review in May 2002. BEPCII main parameters Energy E(GeV)1.89Energy spread(10 -4 ) σ e 5.16 Circumference C(m)237.53Emittance ε x /ε y (nm)144/2.2 Harmonic number h396Momentum compact α p 0.0235 RF frequency f rf (MHz)499.8β * x /β * y (m)1/0.015 RF Voltage V rf (MV)1.5Tunes ν x /ν y /ν z 6.57/7.6/0.034 Energy loss/turn U 0 (keV) 121Chromaticities ν ’ x /ν ’ y -11.9/-25.4 Damping time τ x /τ y /τ z (ms) 25/25/12.5Natural bunch length σ z0 (cm)1.3 Total current/beam I(A)0.91 Crossing angle  (mrad) ±11 SR Power P(kW)110Piwinski angle Φ(rad)0.435 Bunch number N b 93Bunch spacing S b (m)2.4 Bunch current I b (mA)9.8 Beam-beam parameter  x /  y 0.04/0.04 Particle number N t 4.5×10 12 Luminosity(10 33 cm -2 s -1 ) L 0 1.0

7. 7 The BESIII Detector 工 工

8. 8 Main drift chamber Inner diameter: 63mm; Outer diameter: 810mm; length: 2400 mm Inner cylinder: 1 mm Carbon fiber, outer cylinder: 10 mm CF with 8 windows End flange: 18 mm thick Al 7075 ( 6 steps) 7000 Signal wires : 25(3% Rhenium)  m gold-plated tungsten 22000 Field wires: 110  m gold-plated Aluminum Small cell: inner---6*6 mm2, outer--- 8.2 *8.2 mm2, Gas: He + C 3 H 8 (60/40) Momentum resolution (@ 1 GeV/c): dE/dX resolution: 6-7%.

9. 9 85μm

10. 10 EMC: CsI(Tl) crystals 6300 crystals, (5.2x 5.2 – 6.4 x 6.4) x 28cm 3 (15 X 0 ) PD readout, noise ~1100 ENC Energy resolution: 2.5%@1GeV Position resolution: 5mm@1GeV5mm@1GeV Tiled angle: theta ~ 1-3 o, phi ~ 1.5 o Minimum materials between crystals

11. 11 no partition wall Mechanical support structure

12. 12 Super-conducting magnet Al stabilized NbTi/Cu conductor from Hitachi 1.0 T, <5% non-uniformity 921 turns, 3150A @4.5K R = 1.475 m, L=3.52m, cold mass 3.6t Thickness: 1.92 X 0 Inner-winding method

13. 13 Particle ID: TOF system 392 pieces BC408, 2.4 m long, 5cm thick Time resolution 100-110 ps/layer PMT: Hamamatzu R5942 图 3.8.20 桶部光电倍增管的支撑环， 内外两层共 176 个孔。

14. 14  system : RPC 9 layers, 2000 m 2 Bakelite, no linseed oil 4cm strips, 10000 channels Tens of prototypes (up to 1*0.6 m 2 ) Noise less than 0.2 Hz/cm 2

15. 15 Other systems Electronics design have been almost finished, several prototypes have been successfully tested Trigger system largely based on FPGA technology have been designed, prototypes underway DAQ system based on VME/PowerPC and PC farm have been designed, mini-version setup, software underway Offline computing environment based on a large scale PC farm is under study MC based on GEANT4, first reconstruction framework released, sub-detector reconstruction code underway

16. 16 Schedule 5/2004: BESII detector shutdown 11/2004: supporting structure/york installation 3/2005: muon chamber installation 5/2005: magnet installation 10/2005: magnetic field mapping 2/2006: EMC installation 3/2006: MDC/TOF installation 6/2006: Cosmic-ray run 9/2006: BESIII detector in place 12/2006: tuning of detector/machine

17. Physics at BEPCII/BESIII Rich source of resonances, charmonium, and charmed mesons Transition between perturbative and non-perturbative QCD Charmonium radiative decays are the best lab to search for glueballs, hybrids, and exotic states

18. Physics to be studied in  -charm region   Search for glueballs, quark-gluon hybrids and exotic states  Charmonium Spectroscopy and decay properties  Precision measurement of R  Tau physics: tau mass, tau-neutrino mass, decay properties, Lorenz structure of charged current, CP violation in tau decays …  Charm physics: including decay properties of D and D s, f D and f Ds; ; charmed baryons.

19.   Light quark spectroscopy, m c  Testing QCD, QCD technologies, CKM parameters  New Physics: rare decays, oscillations, CP violations in c- hadrons  ….. To answer these physics questions, need precision measurements with High statistics data samples Small systematic errors

20. 20 Event statistics at BESIII Physics Channel Energy (GeV) Luminosity (10 33 cm –2 s –1 ) Events/year J/  3.097 0.6 1.0×10 10  3.67 1.0 1.2×10 7  ’ 3.686 1.0 3.0 ×10 9 D 3.77 1.0 2.5×10 7 Ds 4.03 0.6 1.0×10 6 Ds 4.14 0.6 2.0×10 6 *CLEO took 10 nb D production cross section while we took 5 nb

21. 21 Semi-leptonic decays – one year running Decay Mode Input Br(%) Detection Efficiency Statistics Errors CKM Elements D 0  K - e + e 3.4% 54.6% 0.6 %V cs D 0  K -  +  30.5% D 0   - e + e 0.4% 62.2% 1.6%V cd D 0   -  +  44.3% 8.5% 6.7% 1.6%V cs 3.7%  V cs /V cs = 1.6%,  V cd /V cd = 1.8% E missing -P missing

22. 22 Pure Leptonic decays Decay Modes Decay Constant Branching ratios Life time CKM Elements Precision of decay constants D + →   f D 2.4% 1.2% 1.8% 3.0% D + s →   f Ds 1.7% 1.8% 0.1% 2.5% One year of running

23. 23 Absolute Br measurement: clear D tagging beam energy spread important One year of running

24. 24 Non-leptonic decays Decay Mode Input Br(%) Detection efficiency Statistics Error (  B/B) 3.7 72.2% ~ 0.4% ~7.8 34.0% ~12.0 32.0% ~7.7 52.0% ~ 0.6% 2.8 12.5% ~5.6 9.2% ~8.6 7.9% ~5.0 22.5% D + s →   ~3.0 60.0% ~ 1.2% One year of running

25. 25 B-Factories CLEO-CBEPCII 400 fb -1 3fb -1 5fb -1 Br(D 0 →K -  + ) < 1% Br(D + →K -  +  + ) 3-5% <1% Br(D + s →  -  + ) 5-10% <2% ~ 2% f D >10 % ~2% ~3% f Ds 6-9% ~2% ~2.5% V cs 16% ~1% ~1.5% V cd 7% ~1.5% ~2% Comparison with other facilities *CLEO took 10 nb D production cross section while we took 5 nb One year of running

26. 26 DDbar Mixing at BESIII DDbar mixing in SM ~ 10 –3 - 10 –10 DDbar mixing sensitive to “new physics” Our sensitivity : ~ 10 -4 D 0 D 0  ( K -         Acceptance: ~ 40%  Background: ~ 10 -4

27. 27 QCD and hadron production R-value measurement pQCD and non-pQCD boundary Measurement of  s at low energies Hadron production at J/  ’, and continuum Multiplicity and other topology of hadron event BEC, correlations, form factors, resonance, etc.

28. 28 R-value measurement Error on R  (5) had (M Z 2 ) 5.9% 0.02761 ±0.00036 3% 0.02761 ±0.00030 2% 0.02761 ±0.00029 R-value below 2GeV is important, via radiative return

29. 29 Errors on R at BESIII Error sources BESII (%) BESIII (%) Luminosity 2 - 3 1 Detection efficiency 3 - 4 1 - 2 Trigger efficiency 0.5 Radiative corrections 1 - 2 1 Hadron decay model 2 - 3 1 – 2 Statistics 2.5 -- Total 6 – 7 2 - 3

30. 30 Light hadron spectroscopy Baryon spectroscopy Charmonium spectroscopy Glueball searches Search for non-qqbar states Search for 1 P 1

31. 31 Tau-charm physics after CLEOc? CLEOc begins running now! What important physics issues will remain in 2007? Is the BESIII detector design adequate to address these? There will be a workshop on these issues in January 2004 in balmy Beijing. Workshop will be a CLEOc/BES joint effort. More studies needed before the workshop. Stay tuned. Will post announcement on the QWG web page. Please come.

32. 1.0 T magnet ----9 layers  counter Rich  T (ps) = 100-110/layer Double layer TOF 2.0% 0.3 cm /  E  E/  E( 0 / 0 ) = 2.5 %(1 GeV)  z (cm) = 0.5cm/  E EMC 6%  dE/dx ( 0 / 0 ) = 6 - 7 % 0.5 %  P/P ( 0 / 0 ) = 0.5 %(1 GeV) MDC 90  m  XY (  m) = 130 CLEOcBES IIISubdetector The detector of BESIII and CLEOc

33. 33 International collaboration IHEP, Beijing Beijing University, Beijing Tsinghua University, Beijing USTC, Hefei National Central University, Taipei KEK, Tokyo University, Tokyo Hawaii University, Honolulu Washington University, Seattle More collaborators welcomed

34. 34 Summary The BEPCII/BESIII has been approved officially by the chinese government The initial BESIII detector design is finished, prototyping is underway, mass production is about to start. Rich physics after CLEO-c (upgrade of BEPCII to 3*10 33 cm -2 s -1 is possible) Collaborators are welcomed!