2. Upgrade of PID for BESIII June 13, 2006 Institute of High Energy Physics, Beijing, China Yuekun Heng (hengyk@mail.ihep.ac.cn)hengyk@mail.ihep.ac.cn

3. BESIII Outline  Present TOF design  Physics requirements for PID  Upgrade to MRPC??  Upgrade to Internally reflecting Cherenkov detector: CCT, TOP, Focusing DIRC  Summary and discussion

4. BESIII 1. Present TOF Design

5. BESIII Present barrel TOF The option of barrel TOF is determined after many discussions in June, 2005. Two layers of scintillator will be used for barrel. Barrel TOF Endcap TOF CsI Calorimeter Drift Chamber

6. BESIII Fig. Assembly of barrel TOF. Barrel TOF alignment Fig. BTOF side view. To save space, the base of PMT housing is 6-sides-shaped and the inner and outer layer is across. It has four screws to connect the scin.

7. BESIII Endcap TOF structure

8. BESIII ItemBarrel time reso. Endcap time reso. Intrinsic time reso. of one TOF layer for 1 GeV muon 80~90 ps80 ps Uncertainty from electronics25 ps Uncertainty from bunch length 15 mm ， 35 ps Uncertainty from bunch time~20 ps Uncertainty from Z position5 mm,25 ps10 mm,50 ps Resolution of expected time of flight30 ps Total time reso, one layer of TOF for 1 GeV muon 100~110 ps110~120 ps Total time reso, double layer of TOF for 1 GeV muon 90 ps Analysis of Time reso. Non TOF ~60ps

9. BESIII Why two layers?  Time reso. For Kaon and pion is worse 20% than muon in experiences.  Time reso. Of two layers totally is from 100ps to 110ps for kaon and pion.  That time reso. Can separate kaon/pion of 0.9GeV in the middle of barrel. ContriburionTime reso. For 1GeV Muon Time reso. For Kaon/pion Non TOF60ps One layer of scin. Intrinsic 80-90ps One layer of Scin. Totally 100-110ps110ps-130ps Two layers, Totally 80-90ps100ps-110ps Capability of separation of Kaon and Pion

10. BESIII 2. Physics targets for PID and our space limits

11. BESIII K/πmomentum on BESIII  BEPCII: 2.0~4.2GeV  BESIII: Charm physics:J/Psi, Psi ’, Psi ’’ Tau Physics  K/π momentum: almost all<1.5GeV  K/π seperation: 1.2GeV is enough  Present TOF: 0.9GeV(2sigma,95%) Next target Momentum distribution for hadrons at J/psi

12. BESIII Experimental Searching for D 0 D 0 Mixing (From He Kanglin )  Big challenge to PID (Kπchannel) Main backgrounds come from the double miss-PID  Searching in semi-leptonic decay modes are experimental difficulty with 2 missing neutrino (hard to reduce background contribution to 10 -4 )  Monte Carlo study with different PID (TOF resolution)

13. BESIII Detection efficiency vs TOF resolution

14. BESIII Background rates vs TOF resolution

15. BESIII PID space limits  Banded to MDC outer barrel of Carbon-fiber  R-direction space: 81cm-92.5cm  Scintillator Length: 2320mm  Coverage: ~82% PID space

16. BESIII 3. Upgrade to MRPC??

17. BESIII Target analysis for MRPC  To get 1.2GeV separation of K/pi, totally time reso. <80ps  Non-TOF is 60ps, TOF <60ps, Plastic scin. Can ’ t give so good time. MRPC may be OK.  To cover dead area of MRPC, overlap of two layers of MRPC is needed.  To reduced electronics, MRPC should be long strip and readout by two ends.  Long-strip MRPC needs much more studies.

18. BESIII MRPC results 试验尺寸 cm 时间分辨 VEPPW e+e- 小尺寸 0.1mm 缝隙 75ps （流光模式） NA49 4X30 0.1mm 缝隙） 50ps （流光模式） HARP200X15X1140-180ps FOPI Upgrade 9.1X180 (long strip) 70-80ps （束流试验 ） STAR24X22X9 60ps （束流试验） ALICE120X13X2.538ps Timing RPC R&D 160X10X20 (long strip) 50-75ps 束流试验

19. BESIII III. 4 gaps, 0.3mm/gap HV:10kV/mm Preamp: not say GAS: 85% C2H2F4 5% iso- C4H10 10%SF6 ， 达到的时间分辨为 75ps

20. BESIII MRPC option bakelite as the resis. plate Structure: Resi. Plate: bakelite gaps: 6; Chamber: 8cm(W)X190cm(L) gas ： 90%Freon, 5%iso-butane, 5%SF6 Preamp ： Star Signal pulse HV: 16kV/1.2mm) Readoud pad:3X6cm Rise time:~2ns Time Reso.:70 ～ 110ps The results for a MRPC sample where the fish-line is rolled in longitude direction

21. BESIII Our tests 钓鱼线竖绕板室

22. BESIII 钓鱼线竖绕板室的初步实验结果（吴金杰） Structure: Resi. Plate: bakelite gaps: 6; Chamber: 8cm(W)X190cm(L) gas ： 90%Freon, 5%iso-butane, 5%SF6 Preamp ： Star Signal pulse HV: 16kV/1.2mm) Readoud pad:3X6cm Rise time:~2ns Time Reso.:~110ps Reasons: gap not well

23. BESIII 钓鱼线横绕的 MRPC 实验结果（安正华） 两边气槽和边框共占去 3cm ，有 效面积约 65 ％。

24. MRPC signal

25. BESIII T-Q correction

26. BESIII 14.5kV MRPC: Time reso. 上图是 MRPC 幅度谱在 100 － 400 的时间分辨 由此可计算出 MRPC 的本征时间分辨 sqrt(3.907*3.907-2.837*2.837)*25ps=67.16ps

27. BESIII 14.5kV MRPC 实验总结 时间分辨 上图是 MRPC 幅度谱在 401 － 2047 的时间分辨 由此可计算出 MRPC 的本征时间分辨 sqrt(6.709*6.709-2.926*2.926)*25ps=150.93ps

28. BESIII 4. Internally reflecting Cherenkov detector: CCT, TOP, Focusing DIRC

29. BESIII Cherenkov detectors NamePrincipleRange of PID readout 美国 SLAC Babar － DIRC [2] Quartz + long bar + Water tank + PMT ～ 4GeV11000 PMT ， 日本 KEK BELLE － ACC [3] ACC, Threshold type ～ 3.5GeV 2000 Fine-Mesh PMT 美国 CLEO-III RICH[4] LiF as the radiator,TEA gas to convert photon-electron, MWPC to detect the ring of cherenkov ～ 2.8GeV 230,000 channels electronics CERN LHC-b RICH [5] Two RICHs. RICH1: 5cm thick ACC and 95cm thick C 4 F 10 as radiator;RICH2: 180cm thick CF 4 as radiator ～ 150GeV Hybrid PhotoDiode, Much space CERN LEP DELPHI RICH [6] Gas of C 5 F 12 and liguit of C 6 F 14, as radiator, ~25GeVgas photodetector + MWPC to readout

30. BESIII Internally reflecting cherenkov detector  Using internally reflecting cherenkov light  Parameters to know: track direction Cherenkov light(x,y), or (theta, phi) Transmitting time:

31. BESIII 3 options (refers to Honscheid,Ohshima,Vavra,) CCT(Cherenkov Correlated Timing ) 1D Timing only a) Time is related to cherenkov angle

32. BESIII CCT  Its principle is to measure the time of the cerenkov light to separate particles.  We did simulations. There are about 10 PEs for 2inches PMT with QE of 20%. reso.  Transit time spread of PMT: Line-focus type PMT, 250ps (xp2020) Fine-mesh type PMT, 180ps (R5924) Micro-Channel-Plate type PMT, 50ps (R2809U)

33. BESIII Potential of CCT: MCP-PMT to give good time reso. Refer to:Jochen Schwiening, SLAC T. Ohshima, Nagoya Univ.

34. BESIII Comparison of K/  sep.  TOF+TOF  TOF+CCT Fig. K /  separation for Double TOF Fig. K /  separation for TOF+CCT

35. BESIII TOP: Time of Propagation  Principle: only Φ c andθ c can determine cherenkov angle. TOP and Φ can deduce them.  Quartz bar’s sides are vertical and conserve the Φ c. Quartz lightguide is needed to ensure the light direction out of quartz bar  Fucussing Mirror: fucussing the parrel light because of the thickness of quartz bar.  Photon detector is placed opposite of mirror.  To deduce dead area, the detection end will be placed in opposite ends for adjacent counters

36. BESIII Uncertainties of TOP  Chromatic error. 5 ‰ 。  Uncertainty of Φc. Mirror’s resolution and PMT position resolution, can be 9mrad.  Time spread of PMT  Start time resolution  Thickness of quartz bar. High speed particle transmit quartz bar (20mm) needs about 66ps. But when particle inclined transmits, the uncertainty will be reduced because particle transit time and light transit time lessen it.  Position of injected particle. ~2mm ， ~10ps  Photon electron number Cherenkov ring by Y.Enari Using TOP. Particle 4GeVπ ， position:1m. 2GeVπ ， position:0.02m 和 1m 处. TOP resolution VS Φ.By Ohshima.

37. BESIII TOP: Candidate of Super Belle Refer to Peter Krizan, Super B factory workshop, Frascati, 2006

38. BESIII TOP: For BESIII, 1.2 GeV is enough, 1.5 GeV is very good. Refer to Noriaki Sato, 2005, hawaii

39. BESIII Focusing DIRC Measure the time and 2dimension position It uses APD or MCP PMT to measure the time and position of Cerenkov light from Quartz. No big imaging circles and so no much space is needed. The money is saved because of smaller quantity of PMT.

40. BESIII Candidate of Babar ’ s next plan From Vavra, Hawaii workshop

41. BESIII 5. Summary  1.2GeV K/Pi separation is needed for BESIII physics. Now it is only 0.9GeV. Upgrade is nessesary.  <60ps of Long-strip MRPC is OK to give 1.2GeV separation. Experiments is under way. 60ps is not easy.  CCT has good potential for the upgrade. It is simple with MCP-PMT of good time reso.  TOP can give over 1.5GeV separation of K/pi.  Focusing DIRC needs more space, impossible for BESIII

42. BESIII The End Thanks a lot!

43. BESIII K/Pi difference of cherekov light