1. Event Start Time Determination Ma Xiang 2005.12.14

2. 内容 1. 修改 MdcFastTrkAlg, 修改过程及修改后结 果，包括效率，分辨率等 2.TOF 端盖部分算法设计，用 MC 数据检验 的结果 3.MDC 部分算法，用 MC 数据检验的结果 4. 总结

3. 1.MdcFastTrkAlg (1)When track angle cosθwithin 0.84-0.94,the tracking efficiency less than 20%. Fast Tracking must be modified to suite the END cap case. * Due to superlayer 0,5,7 slant is wrong in the code, hits on those layers can’t be used in the tracking. ( slant 0,5,7 is -,1,6,8 is + in Geometry, but all are + in code) * If track can not reach axial segment 9 &10, cut the requirements for Seg.9 &10. * Min. requirements only one stereo segment. (Normal case: 6 stereo Seg. 5 axial seg.) After modification the tracking efficiency achieve over 90% for single particle with1.5Gev.

4. Quality checking between the old and new e -, 1.5Gev,2000,cosθ ∈ (0.85,0.94) Old Code efficiency: 5.3% Modified efficiency: 89%

5. Quality checking between the old and new P Resolution old cosθ(-0.8,0.8) p:1.497Gev/c σ:0.022 P Resolution new cosθ(0.85,0.94) p:1.491Gev/c σ:0.124

6. Quality checking between the old and new XY 空间分辨 cosθ(-0.8,0.8) 136μm XY 空间分辨 cosθ(0.85, 0.94) 180μm

7. Quality checking between the old and new Z 空间分辨 z 空间分辨 cosθ(-0.8,0.8) 5mm z 空间分辨 cosθ(0.85,0.94) 9.3mm

8. 2.End-cap TOF Check 2* helix_ radius > R_tof in xy plane?  Yes, an intersection in xy plane =>calculate Z_tof, if Z_tof >120cm(<-120cm), assume hit on EndTOF, calculate TOF ID, if ID matches MC, calculate evtime A Barrel TOF End-cap TOF. A x y Barrel TOF z y

9. End-cap TOF  No, no intersection in x-y plane, =>if tanl>0, assume hit on endTof: whether TOF ID matches? If matching, calculate evtime =>if tanl<0, assume hit on End-cap TOF: whether TOF ID matches? If matching, calculate evtime Barrel TOF x y. A Helix

10. Result e-,1.5Gev,2000 MC data, cosθ ∈ (0.85,0.94) t 0 : -0.0048ns σ: 0.29ns End-cap TOF

11. Single match multi matches End-cap TOF (e-,0.3Gev,2000, cosθ ∈ (0.85,0.94)) Entries:741 t 0 : 0.044ns σ: 0.397ns Entries:1365 t 0 : 0.092ns σ: 0.649ns

12. Sense wire Field wire Drift cell A (t est ) B C D 3. ESTime Calculation by MDC 根据 MDC 快速 重建结果计算 常数  T est = TDCM － t ev

13. 1.t drift :  Axial segments  Stereo segments 2.t f :  Axial segments  Stereo segments e-,1.5Gev,3000,MC t0: 0.08ns σ:3.49ns T est = TDCMC － t ev ~~~~~~~~~~~~~~

14. 总结 1. 修改 MdcFastTrkAlg ，提高了 TOF 端盖部分径 迹重建效率，但空间分辨和动量分辨变差 2.TOF 端盖部分算法基本完成，时间分辨达到 要求 3.MDC 部分算法，还需要完善