BESIII 宇宙线实验 朱科军 高能物理研究所

BEPCII Project Luminosity: 3~10×10 32 cm -2 s 3.77GeV

Milestones Barrel EMC and electronics was ready on 11/30/2007 Trigger system for EMC was ready on 11/30/2007 Started MUON test since 12/3/2007 Barrel TOF and electronics was ready on 12/20/2007 MDC and electronics was ready on 1/2/2008 Cosmic ray w/o end-cap seen on 1/6/2008 End-cap of EMC and TOF was ready on 2/12/2008 Cosmic ray with full detector seen on 2/14/2008 Cosmic ray data taking finished on 3/16/2008 Moved to the BEPCII IR by mid-April, 2008 Data taking is expected around mid-June, 2008.

System overview

触发条件和定时  00 to 15 :::::: EMC  00 : NCluster >= 1  01 : NCluster >= 2  02 : Barrel Cluster back to back  03 : Endcap Cluster back to back  04 : Cluster Balance in Z direction  05 : Barrel Cluster Balance in Phi direction  06 : Endcap Cluster phi Balance  07 : Barrel total Energy Higher threshold  08 : Endcap total Energy Higher threshold  09 : total Energy Lower threshold  10 : total Energy Middle threshold  11 : Energy Balance in "Z" direction  12 : Barrel Energy difference Balance  13 : Endcap Energy difference Balance  14 : Energy Block Balance  15 : Endcap Energy Balance  16 to 21 :::::: TOF  16 : Endcap TOF back to back  17 : Barrel TOF back to back  18 : NETOF >= 2  19 : NETOF >= 1  20 : NBTOF >= 2  21 : NBTOF >= 1 (0x15)  32 to 37 :::::: MUON  32 : MUON Back to Back 3478  33 : MUON Back to Back 37  38 to 47 :::::: MDC  38 : Short Track back to back  39 : NStrk >= N  40 : NStrk >= 2  41 : NStrk >= 1  42 : Long Track back to back  43 : NLtrk >= N  44 : NLtrk >= 2  45 : NLtrk >= 1  46 : NItrk >= 1  47 : NItrk >= 2

触发道  0x1=> EMC Ncluster >= 1  0x2 => NBTOF >= 1  0x4 => BTOF back to back  0x8 => EMC Cluster back to back  0x10 => Short Track Back to Back  0x20 => Long Track Back to Back && BTOF Back to Back  0x100 => BTOF back to back && Ncluster >= 1  0x200 => random trigger  0x400 => Long Track Back to Back && NCluster >= 1  0x800 => NLtrk >= 1  0x1000 =>MUON Back to Back 3478  0x2000 => MUON Back to Back 37  0x4000 => NBTOF >= 1 && NClus >= 1  0x8000 => NLtrk >= N

Run2414: :17 to :00 Trigger channels: 0x441c Endcap Cluster phi Balance Long Track Back to Back && NCluster >= 1 ETOF back to back EMC Cluster back to back BTOF back to back Timing: 0x8022a11 Barrel TOF back to back Long Track back to back Barrel Cluster back to back

时间低阈的选取 在 3# 厅进行的宇宙线测试中，按噪声水平 1% 为标准，设置的时间低阈为 内室 110 ； 台阶 70 ； 大端板 50 内室 120 ； 台阶 80 ； 大端板 60 ( 数据分析得到的理想低阈 ) 当前条件下，如果按 1% 的标准，时间低阈应为 内室 100 ； 台阶 70 ； 大端板 40 随机触发，设置时间道高低阈相等，在不同时间阈值下测量漂移室各通道的时间计 数，计数值阈触发数之比反映了漂移室在该时间阈下的噪声计数水平

Hitmap and distribution of T and Q (run1963) T hitmapQ hitmap T distributionQ distribution

Drift distance (mm) Drift time (ns) Time-to-distance relation (layer 12) Drift time (ns) Entries Distribution of drift time (layer 12) Results of calibration and reconstruction

Spatial resolution (after calibration and alignment) HV: 2150V T threshold: 120/150(inner section), 80/110(stepped section), 60/80(outer section)

Spatial resolution vs layer

Efficiency vs layer

TOF Calibration Using Cosmic Ray Data

Time Difference of Each Counter The distribution of sum time of two end. The fitting function is Error Function. Mean value vs counter number Sigma value vs counter number

T0 Extract σ=317psσ=164ps σ=283ps Original T0 T0 after calibration T0 Difference before and after T0 extract Delta T distribution before and after T0 extract

Single End Readout Time Resolution (Preliminary!) East and West end readout time resolution with unit/ps Using time difference of each counter and T0 extraction, with an approximation of β ＝ 0.99, the single end readout time resolution are shown.

event Selection –EMCb2b –Energy of digi>10MeV, and only two digis Check ADC(MeV) distribution for each crystal –First calibrated by using relative light yield data, –and comparison with the MCdata Finally give the Preliminarycalibration constant for every crystal How to calibrate by using cosmic rawdata

Hitmap of sample events

宇宙线事例： EMC b2b 触发 选择只击中两块晶体的事例

ADC (MeV) vs nphi Barrel light yield by PMT PMT RLY calibrationNo calibration

No-calib Sig/mean= 32.57/239.7=13.6% PMT RLY calib Sig/mean= 26.95/265.8=10.1% Cosmic RLY calib Sig/mean= 29.59/265=11.2% Fiber RLY calib Sig/mean= 29.01/262.3=11.1% Barrel_all Preliminary results only using relative light yield data Gaus_landau fitting

adc2-28l-2930 Mean=267MeV Phi=29&30 Mean/RMS= 187.6/19.55 RawData MCData C1=Mean_mc/Mean_raw~188/267=0.7 First calibration by Cosmic rawdata

Cosmic_mcCosmic_rawdata, barrel_all The22&phi29 Sig/mean= 11.38/182.1 =6.25% Barrel_all Sig/mean= 12.34/184.4 =6.7% Only relative light yield by PMT test Sig/Mean=27/265.9 =10.1% relative light yield by PMT test +mc_calib Sig/Mean=16.7/183.4 =9.1% Preliminary results using relative light yield data & MC_calib

Barrel_allBarrel_28cmBarrel_24cm Barrel_ntheta2 1 Barrel_nthe21& nphi29 Cosmic Rawdata 32.57/239.7= 13.6% 32.56/239.6 =13.6% 27.57/247.7 =11.1% 22.84/228.7 =10% Relatvie light yield calib(PMT) 27/265.9 =10.1% 26.63/266.2 =10% 21.28/216.1 =9.85% 24.97/266.8 =9.36% 26.5/293.9 =9% Relatvie light yield calib(PMT) +mc_calib 16.7/183.4 =9.1% 16.52/183.6 =9% 15.23/158.3 =9.6% 16.23/182.4 =8.9% 16.55/183.6 =9% Mc simulation 12.23/184.2= 6.64% 11.93/184.3 =6.47% 10.95/158.4 =6.91% 11.75/183.1 =6.42% 6.25% Sigma/mean by Gaus+landau fit Preliminary results

By layer By segment Hit map Hit maps show pretty well, noise and dead channel have been checked and repaired

Counting rate Trigger rate: 75~90Hz, Counting rate of MUC at Hz/cm 2 level

总结 BESIII 宇宙线调试总的来说进展顺利 已获取一定数量的宇宙线事例供离线进 行软件调试和探测器性能的初步研究， 帮助查找硬件中存在的问题 下月初进行第二轮宇宙线测试 准备迎接对撞取数

谢谢