Motivation BESIII BESIII ETOFEJ 204 R 5924 PMT

Motivation BESIII • 现有的 BESIII E-TOF：EJ 204闪烁体 + R 5924 PMT TOF 模块 431 mm (闪烁体) PMT μ: 110 ps e: 148 ps (本征: <80 ps) π: 138 ps Apr. 24, 2014 平均 2σ π/K 分辨 达到 p. T = 1 Ge. V/c 核探测与核电子学国家重点实验室 2014 年年会，北京 3

Motivation BESIII • 电子在MDC和E-TOF之间发生多重散射 • 次级粒子造成多重击中 • 基于位置的时间刻度难以进行 需要更小的读出单元 ZHANG Hui , A GEANT 4 simulation study of BESIII endcap TOF upgrade, Chinese Physics C Vol. 37, No. 9 (2013) 096002 Apr. 24, 2014 核探测与核电子学国家重点实验室 2014 年年会，北京 4

束流测试 不同动量下的性能 BESIII • 低动量proton有更高的能损 • 在气隙中有更高的电离密度 • 更好的时间分辨 Pion (MIP) Proton 800 Me. V 600 Me. V 500 Me. V 400 Me. V simulation Ming Shao, Simulation study on the operation of a multi-gap resistive plate chamber, Meas. Sci. Technol. 17(2006) 123– 127 Apr. 24, 2014 核探测与核电子学国家重点实验室 2014 年年会，北京 13

The energy loss of proton (simulation) BESIII p p The simulation indicates significant energy loss on the materials, especially for the low momentum protons. The main energy lost occurred on the MRPC materials (not Al box). Total Lost: ~150 Me. V/c Apr. 24, 2014 # 1 # 2 # 3 Total Lost: ~100 Me. V/c 核探测与核电子学国家重点实验室 2014 年年会，北京 20

The contribution from the energy loss BESIII Measured: σ=46. 5 ps simulation: σ=24 ps The time resolution results of before and after removing the contribution from the energy loss. proton 500 Me. V 600 Me. V (p 2) Before After M 1 36 ps 30 ps 34 ps 32 ps 34 ps 33 ps M 2 23 ps 27 ps 29 ps 30 ps 34 ps 35 ps M 3 41 ps 34 ps 33 ps 31 ps 35 ps 33 ps Apr. 24, 2014 核探测与核电子学国家重点实验室 2014 年年会，北京 21

counts BESIII 67 ps 42 ps T-Tr Apr. 24, 2014 T-Tr 核探测与核电子学国家重点实验室 2014 年年会，北京 27