北京谱仪Ⅱ带电径迹测量误差矩阵的修正

BESⅡ Error Matrix Correction on Charged Channel

研究了北京谱仪 (BES)Ⅱ带电径迹测量误差矩阵的修正 ,使运动学拟合TELESIS方法在BESⅡ物理数据分析中得到应用 .1)在BESⅡ数据重建程序中 ,加入了适当的MDC重建单丝分辨率 (2 5 0 μm)和Q修正 .2 )在TELESIS程序中 ,放入了BESⅡ有效物质量对BESⅡ误差矩阵进行多次库仑散射和dE/dX能损效应的修正 .3)在此基础上 ,通过J/ ψ→μ+ μ-的数据样本分析 ,完成了BESⅡ 2 4× 10 6J/ ψ事例RUN by RUN的误差矩阵刻度 ,同时对BESⅡMC数据也作了相应的刻度 .经上述误差矩阵修正后 。

The error matrix correction for charged track parameters of BESⅡ detector is carefully studied. The proper MDC wire spatial resolution ( σ =250μm) and Q correction are incorporated into BESⅡ data reconstruction program. The BESⅡ effective material passed through by tracks from interaction point to MDC is taken into account in the kinematics fitting package TELESIS,to correct the multiple scattering and d E /d X energy loss effects. By analyzing the J/ψ→μ +μ - data sample,the RUN by RUN error matrix calibration is completed for BESⅡ 24×10 6 J/ψ events. After these corrections of the error matrix,TELESIS can be applied to BESⅡ J/ψ data analysis with fairly good accuracy.