BESIII Physics and Detector Overview International BESIII Workshop Weiguo Li

1. BESIII Physics and Detector Overview International BESIII Workshop Weiguo Li IHEP, Beijing, Oct. 13, 2001

2. BES Detector and Physics Achievements • Physics at BEPCII/BESIII • BESIII Detector Overview • Summary

3. BESII Detector and physics achieved VC: xy = 100 m BTOF: T = 180 ps (>330 ps) MDC: xy = 250 m BSC: E/E= 20 % ,z= 3.0 cm dE/dx= 8.4 %  counter: z = 5.0 cm DAQ readout < 10 ms

4. Major parameters of the BES detector performance Detector Major para. BESI BESII VCx,y (m) 200 100 MDCxy (m) 200-250 ~220 p/p (%) 1.78 (1+p2) 1.7 (1+p2) dE/dx(%) 7.9 8.4 BTOFT (ps) 375 180 BSCE/E (%) 23.8 20.3 z (cm) 4.5 3.0 Muonz (cm) 5.0 5.0 DAQdead time/event (ms) 20 <10 BESII from 1996

5. Data Collected with BESIand BESII

6. World J/ and (2S) Sample (106) Largest from BES J/ (2S) 2001

7. The BES Collaboration Korea (3) Korea University Seoul National University Chonbuk National University USA (4) University of Hawaii University of Texas at Dallas Colorado State University Stanford Linear Accelerator Center UK (1) Queen Mary University Japan (4) Nikow University Tokyo Institute of Technology Miyazaki University KEK China (15) 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.

8. BES Entries in PDG 2000

9. Topics Citations BES detector 42 τ 170 J/ψ 82 ψ’(хc) 146 D、DS 51 R 6 Total 492 Citations of BES Papers

10. High Lights of BES Physics Results • Precise τ mass measurement MeV/c2 • 2-5 GeV R measurement, better prediction for Higgs mass, 61  90 GeV, upper limit 170  210 GeV • J/ψ physics, hadron spectroscopy, search for glueball, hybrids and exotics • ψ(2s) physics, new measurements of ψ(2s) and c decays, 15% rule,  suppression • DS 、D physics, leptonic, semileptonic and absolute Brs;

11. Recentpreliminaryresults: • Study of the structure around 1.7 GeV mass region in J/  K+K- , to be 0++ state • Systematic study and PWA analysis of J/  +-, K+K- ,+-, K+ K- ,+-, K+K- • Analyses the properties of  from J/  +- • Study of excited baryonic states (N*, *…) - Pureisospin 1/2 -Largebranching ratio ~10-3 More results are expected with 50M J/ events

12. First Measurement of B((2S)+-)(hep-ex/0010072) • B((2S)+-) =2.710.43 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

13. Scan of (2S) peak 24 energy points between3.67and3.71 GeV Int. L = 760 nb-1 Improve the parameters of (2S) , B(h), B(+ -), B(+-J/) B(+-X)

14. Running Plan before 2004 BEPC will take data withBESII at least until2004 - 12 M(2S) events/year - Precision measurement of R in 2-3 GeV - (3770)? Afterwards, a long shutdown will be scheduled for the installation of BEPC II.

15. Physics to be studied at -charm region Search for glueball, quark-gluon hybrid and exotic states; • Charmonium Spectroscopy and decay properties; • Precision measurement on R value; • Tau physics: tau mass, tau-neutrino mass, decay property, Lorenz structure of charged current, CP violation in tau decays … • Charm physics: including decay properties of D and Ds, fD and fDs , D0 –D0 mixing and CP violation…

16. To answer these physics questions, key issue is precision measurements with • High statistics data samples • Small systematic errors  Future development of BEPC/BES: • High luminosity machine • High performance detector: • adapts to high event rate • provides small systematicalerrors

17. From BESII to BESIII • The Shortcomings of BES II Detector • Poor energy resolution for electrons and photons; • Marginal charged track momentum resolutions; • TOF counters too wide, multiple hits in one counter; • Information from endcap detector is not sufficient for • phys. analysis; • Endcap not easily openable to fix detector problems; • Muon coverage too small.

18. Upgrades Needed for BEPCII/BESIII • BEPCII with multi bunches and smaller beam size, • BES needs: • Upgrade DAQ system with pipeline scheme, to accommodate a factor of more than 200 event rate; • As the beam size (Z) reduced from 4-5 cm to 1-1.5 cm, there is room to further improve TOF time resolution. Generally speaking, as the statistical errors become smaller with larger samples at BEPCII, a better detector is needed to improve the systematic errors, BESIII will be almost completely a new detector.

19. Physics at BEPCII/BESIII • Rich 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

20. Particle Energy Single Ring（1.2fb-1） Double Ring (4fb-1) D0 ’’ 7.0106 2.3107 D+ ’’ 5.0106 1.7107 DS 4.14GeV 2.0106 0.72107 +- 3.57GeV 3.67GeV 0.6106 2.9106 0.2107 0.96107 J/ 1.6109 6109 ’ 0.6109 2109 Expected Event Rates/Year at BES III

21. J/ψ Physics • 1. Glueball search • criteria for glueballs: • no place in nonet • enhanced production in gluon rich processes • decay patters incompatible with states • reduced   couplings • masses, quantum numbers consist with lattice QCD Candidates for glueballs: f0(1500), fj(1710), (2230) , etc.,

22. Red ordinary Green interesting non- states Black other states not fitting in

23. Lattice QCD Numerical Calculation of Glueball Masses 0++ IBM 1740  71 MeV (1994)  1632 49 MeV (1998) UKQCD 1568  89 MeV (1993)  1611  30  160 MeV (1998) improved 1600  100 MeV (1997)  1730  50  80 MeV (1999) IHEP(Wu) 1757  100  86 MeV (2001) 2++ Meachel 2332  88 MeV (1989) UKQCD 2270  100 MeV (1993) IBM 2359 128 MeV (1994) Morningstar 2140  45 MeV (1997) Morningstar 2400  25 120 MeV (1999) IHEP(Wu) 2417  84 117 MeV (2001)

25. 2. Hunting for hybrids Searching for states with exotic quantum numbers, 0+-, 0--, 1-+, 2+-, 3-+,…… J/ψ  x, x  or 5, or 0, or 3 J/ψ  x, x(1300) or a1(1260) or KK1(1400) with (1300) and a1(1260) decay to   3. Other interesting topics Nature of f0(980) Searching for glueballs and hybrids throughψ(2s)   c

26. Searching for 1-+ state producing J/ψ  x, x 0, X are mixing of f0(980), a2(1320), (1390), (2300), here (1390) is 1-+ state

28. ψ(2S) Physics • BESII may collect 1.6  107ψ(2S) events. • and BESIII 2  109 ψ(2S) events/year. • Hadronic decays, systematic study of decays with better BR measurements, 15% rule, VP, VT and other modes • BR uncertainty 10-30% a few % • Radiative decays, search for glueballs, etc • cdecays, systematically measure BR • BR uncertainty 10-30% a few % • Upper limits will be improved by two orders

29. search • Assuming the Br is the same for and c • with 3 109ψ(2s), fast simulation shows, using 3 2P in • -------------- • about 600 signal events can be selected, and there are about • 12 background events from corresponding c decays. • 1P1 search • From ψ(2s)  0 1P1    c    4K • with 3 109ψ(2s),fast simulation shows, • about 250 signal events can be detected, with about 8 background events.

31. Signal for (598) background(12) With 3 109 ψ(2s) produced

33. Signal for 1P1 (248) background(8) With 3 109 ψ(2s) produced

34. Charmed Meson Physics • Low background, simple events, using D, Ds tagging, • can have lower systematic errors to study • Pure leptonic decays. fD ,fDs • Semileptonic decays , • Non-leptonic decays • One year run at (3770) or 4.03 GeV, a few percents statistically • mixing through ( ) ( ) Lower statistics compared with B factories Need careful study to evaluate physics reaches and make comparison

35. Decay Input Measured Stat. Stat. Total Mode Value Value Error Error Error 80 pb-1 80 pb-1 1000 pb-1PDG 3.7 3.590.15 4.2% 1.2% 2.3% 7.8 8.120.34 4.2% 1.2% 4.1% 7.7 7.800.40 5.1% 1.4% 6.7% 2.8 2.990.17 5.7% 1.6% 9.0% 5.6 5.160.32 6.2% 1.8% 12.8% 0.69 0.750.05 6.7% 1.9% 8.0% 3.4 3.330.17 5.1% 1.4% 4.9% 0.4 0.370.06 16.2% 4.6% 16.2% 7  3 events 90 10 events for 1000 pb-1(4000 pb-1/y)

36. With one side semi-leptonic decay, the other tagged D mass distribution

38. τ Physics • Threshold production, without open charm background • one year data taking at 3.57 GeV or 3.67 GeV will produce • about 2-10 million τ events, with small backgrounds • CP violation in τ decays, with 427 pure leptonic decay e events collected at 4.03 GeV, A  a few percent • more events( a factor of ~100) and more decay channels will give better results • precise τmass and τ neutrino mass measurement • τ Decay studies

39. Study Baryonic Excited States (N*, * , * and * ) from J/ψ and ψ(2s) Decays • Complementary to experiments at CEBAF, GRAAL • and SPRING8 • Can systematically study the excited bayrons • Can reveal the quark-gluon structure of matter

40. Re-measure R-values in BEPC Energy Range The contribution to the (MZ2) from R-value remains to be significant. After R values at lower energy get measured accurately, from VEPP-2M in Novosibirsk and  factory in Frascati (~1%level), it is worth while making the R measurement in BEPC energy range with an uncertainty of ~3%, should check if 1% level is possible? . Should try to maintain this possibility in the design of BEPCII. • Study of QCD and hadron production in BEPC energy region

41. The Impact of BES’s New R-Values on the SM Fit

43. Searches and Possible New Physics • Lepton flavor violating J/ψ decays • J/ψ  e, e,   • J/ψ decay to D+X • CP violation in J/ψ decays • With more than109J/ψand ψ’ events, the upper limits for rare and forbidden decays, • Br measurements can reach the level of 10-6~10-7

44. At Hadron2001 held in Protvino of Russia, • Fermilab pbar p experiment admitted that, the signals of • 1P1 and are not confirmed, with a factor of 3 more luminosity than before. • VES stated that the 1-+ signal of 1(1400) found before, should be explained • as the feed down of the nearby peak, for 1(1600) there is still possibility it is • a 1-+ state, but VES played down the significance. • On the other hand, BNL E852 still hold the 1-+ signals are true. • So the situation becomes more uncertain, it gives BES more • chance to make discoveries, but it also tells that the hadron • physics is very complicated.

45. BESIII Detector Overview According to the current plan, among the detector components, almost every component Should be replaced with new detector. The new detector design is very much affected by using retired L3 BGO crystals as the barrel calorimeter.

47. Schematic of BESIII detector

48. Major Upgrades in BESIII • Superconducting magnet • Calorimeter: BGO with E/E ~ 2.5 % @ 1GeV • MDC IV: with small cell, Al wires and He gas • Vertex detector: Scintillation fibers for trigger • Time-of-flight : T ~ 65 ps • Muon detector • New trigger and DAQ system • New readout electronics

50. Scintillating fiber for Trigger 1.27 mm or thinner Be beam pipe may be used • R ~ 3.5 cm • 2 double-layers: one axis layer and one stereo layer • Scintillating fiber: 0.3*0.3 mm2, L~60 cm • Clear fibers: 0.3*0.3 mm2, L~1.4 m • two side readout by APD (Φ3) (below –300) • Signal/noise: <6 p.e.> / <~1p.e.> • ~ 50 m z~ 1mm • Total # of channels: 27 x 8 = 216