Nov 27th, 2007 Yuekun Heng (hengyk@mail.ihep.ac.cn) IHEP PID detector on BESIII Nov 27th, 2007 Yuekun Heng (hengyk@mail.ihep.ac.cn) IHEP Now I will introduce the TOF detector on BESIII.
Outline Physics requirements for PID Present TOF design Upgrade to MRPC?? Upgrade to Internally reflecting Cherenkov detector: CCT TOP Focusing DIRC Summary and discussion
1. Physics requirements for PID
K/πmomentum on BESIII Momentum distribution for hadrons at J/psi BEPCII: 2.0~4.2GeV BESIII: Charm physics:J/Psi, Psi’, Psi’’ Tau Physics K/π seperation: 0.9GeV is generally OK 1.2GeV is needed of some topics 1.5GeV is good enough Present TOF: 0.9GeV(2sigma,95%) Momentum distribution for hadrons at J/psi
Searching for D0D0 Mixing By Kπchannel: Big challenge to PID Main backgrounds come from the double miss-PID By semi-leptonic decay: difficulty with 2 missing neutrino (hard to reduce background contribution to 10-4) Monte Carlo study with different PID (TOF resolution) (by He Kanglin )
2. Present TOF Design
Present TOF: 90 ps 90 ps: almost the limits for scin. for 2m length Table. TOF based on scin. Exp. year Scin. L X W X T(cm) PMT Reso.(ps) DELPHI 1990 NE110 350 X 20 X 2 EMI19902KB 1200 NNbar 1992 (210-300) X 21 X 2 XP2020 300 CLEOII BC408 280 X 10 X 5 139 OBELIX 1995 300 X 9.3 X 4 170 NA49 2000 (12-48)X(1-1.25) X(1.5–2.4) R3478 80 DIRAC 2002 BC420 40 X 7 X 2.2 R1828-01 123 BELLE 255 X 6 X 4 R6680 90ps CDFII 2003 279 X 4 X 4 R7761 100 HARP 2004 (180-250) X 21 X 2.5 160
Capability of separation Why two layers? Capability of separation of Kaon and Pion Much uncertainty from NON TOF contribution like bunch length and time etc. Time reso. For Kaon and pion is worse than muon 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. Contribution Time reso. For 1GeV Muon Time reso. For Kaon/pion Non TOF 60ps One layer of scin. Intrinsic 80-90ps One layer of Scin. Totally 100-110ps 110ps-130ps Two layers, Totally 100ps-110ps
Beam tests of Prototype TOF prototype : scin.、PMT preamp、18m cable and electronics Particles: π, p, e Analysis： position correction, time walk correction double particles Pion:104±11ps proton:70±2ps Electron:94±3ps 图. 束流实验框图
Installation just finished 图. 安装后信号：噪声<10mV、前沿～5ns 图. 安装过程示意图
3. Upgrade to MRPC??
Target for MRPC with long pad: 60ps TOF of MRPC: 60ps. totally time reso. <80ps to get 1.2GeV separation of K/pi, Non-TOF is 60ps, ALICE’s and STAR’s MRPC with small pad: <60ps. Long-strip MRPC needs much more studies. Example 1. Italian EEE project:
Example 2. 75ps HV: 10kV/mm GAS: 85% C2H2F4 5% iso- C4H10 10%SF6， 4 gaps, 0.3mm/gap HV: 10kV/mm GAS: 85% C2H2F4 5% iso- C4H10 10%SF6， Results: 75ps
Manufacture of MRPC with long pad Bakelite type: made and tested and canceled reason: un-uniformity of 1mm bakelite influence electronic field much Glass type: T(1mm) by L(1m) Components of China-made glass 图. MRPC结构 图. 制作过程非常繁琐：测试清洁玻璃、制作电极、PCB板粘接到蜂窝板、安装尼龙柱、绕钓鱼线、安装高压电极、安装玻璃、安装高压电极、安装信号引出等等10多项步骤。
Preliminary results from cosmic ray tests Eff.>95%, Reso.～100ps Fig. Eff. VS HV Fig. Time resolution. Fig.Time reso.VS HV Fig. Single Rate VS HV
4. Internally reflecting Cherenkov detector
3 options (refers to Honscheid ,Ohshima, Vavra,) CCT(Cherenkov Correlated Timing ) 1D Timing only a) Time is related to cherenkov angle
CCT simulation (by Chunxiu Liu) Charged particle 87cm By SLAC MCP-PMT(85001-501) Photocathode square 2 in Spectra Range 165-660 nm Rise Time 0.3 ns Pulse Width (FWHM) 1.8 ns Transit Time 3 ns Transit Time Spread 30 ~ 50 ps Model Gain 0.6106 By Nogoya Univ.
PMT Response time response for SPE Time of Photoelectron rise time=0.3ns time response for SPE Signal of Single PE Pe number Time of Photoelectron Time(ns) PMT signal pulse Voltage(mV) Time(ns)
Threshold :40mV~5photonelectron CCT: Seperation of K/ Threshold :40mV~5photonelectron 1.0GeV 0.8GeV 1.2GeV 1.5GeV K/ seperation(3) K/ seperation(2) cos Time Diff of k/ (ns) CCT (intrinsic)
5. Summary Physics requirements for K/ separation on BESIII: 0.9GeV is general OK 1.2GeV is needed for some topics 1.5GeV is good enough Present TOF: 90ps is reached from beam tests and almost the limit of scintillator TOF. BESIII is made of two layers of TOF. MRPC with long-pad, target: 60ps; Prototype is made Preliminary result: 100ps. Internally reflecting Cherenkov detector: CCT has good potential for the upgrade. Simulation show it can give 1.2 GeV K/ separation TOP is another option, refer to PID upgrade for BELLE. Focusing DIRC needs more space, impossible for BESIII
The End Thanks a lot!
K/Pi difference of cherekov light