Position reconstruction and surface background model for the PandaX-4T detector
Creators: name: Qian, Zhicheng
name: Gu, Linhui
name: Cheng, Chen
name: Bo, Zihao
name: Chen, Wei
name: Chen, Xun
name: Chen, Yunhua
name: Cheng, Zhaokan
name: Cui, Xiangyi
name: Fan, Yingjie
name: Fang, Deqing
name: Gao, Zhixing
name: Geng, Lisheng
name: Giboni, Karl
name: Guo, Xunan
name: Guo, Xuyuan
name: Guo, Zichao
name: Han, Chencheng
name: Han, Ke
name: He, Changda
name: He, Jinrong
name: Huang, Di
name: Huang, Houqi
name: Huang, Junting
name: Hou, Ruquan
name: Hou, Yu
name: Ji, Xiangdong
name: Ji, Xiangpan
name: Ju, Yonglin
name: Li, Chenxiang
name: Li, Jiafu
name: Li, Mingchuan
name: Li, Shuaijie
name: Li, Tao
name: Li, Zhiyuan
name: Lin, Qing
name: Liu, Jianglai
name: Lu, Congcong
name: Lu, Xiaoying
name: Luo, Lingyin
name: Luo, Yunyang
name: Ma, Wenbo
name: Ma, Yugang
name: Mao, Yajun
name: Meng, Yue
name: Ning, Xuyang
name: Pang, Binyu
name: Qi, Ningchun
name: Ren, Xiangxiang
name: Shan, Dong
name: Shang, Xiaofeng
name: Shao, Xiyuan
name: Shen, Guofang
name: Shen, Manbin
name: Sun, Wenliang
name: Tao, Yi
name: Wang, Anqing
name: Wang, Guanbo
name: Wang, Hao
name: Wang, Jiamin
name: Wang, Lei
name: Wang, Meng
name: Wang, Qiuhong
name: Wang, Shaobo
name: Wang, Siguang
name: Wang, Wei
name: Wang, Xiuli
name: Wang, Xu
name: Wang, Zhou
name: Wei, Yuehuan
name: Wu, Weihao
name: Wu, Yuan
name: Xiao, Mengjiao
name: Xiao, Xiang
name: Xiong, Kaizhi
name: Xu, Yifan
name: Yao, Shunyu
name: Yan, Binbin
name: Yan, Xiyu
name: Yang, Yong
name: Ye, Peihua
name: Yu, Chunxu
name: Yuan, Ying
name: Yuan, Zhe
name: Yun, Youhui
name: Zeng, Xinning
name: Zhang, Minzhen
name: Zhang, Peng
name: Zhang, Shibo
name: Zhang, Shu
name: Zhang, Tao
name: Zhang, Wei
name: Zhang, Yang
name: Zhang, Yingxin
name: Zhang, Yuanyuan
name: Zhao, Li
name: Zhou, Jifang
name: Zhou, Jiaxu
name: Zhou, Jiayi
name: Zhou, Ning
name: Zhou, Xiaopeng
name: Zhou, Yubo
name: Zhou, Zhizhen
Publisher: name: arXiv
Year: 2025
Subjects: subject: Instrumentation and Detectors (physics.ins-det)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report the position reconstruction methods and surface background model for the PandaX-4T dark matter direct search experiment. This work develops two position reconstruction algorithms: template matching (TM) method and photon acceptance function (PAF) method. Both methods determine the horizontal position of events based on the light pattern of secondary scintillation collected by the light sensors. After a comprehensive evaluation of resolution, uniformity, and robustness, the PAF method was selected for position reconstruction, while the TM method was employed for verification. The PAF method achieves a bulk event resolution of 1.0 mm and a surface event resolution of 4.4 mm for a typical $S2$ signal with a bottom charge of 1500 PE (about 14 keV). The uniformity is around 20\%. Robustness studies reveal average deviations of 5.1 mm and 8.8 mm for the commissioning run (Run0) and the first science run (Run1), respectively, due to the deactivation of certain PMTs. A data-driven surface background model is developed based on the PAF method. The surface background is estimated to be $0.09 \pm 0.06$ events for Run0 (0.54 tonne$\cdot$year) and $0.17 \pm 0.11$ events for Run1 (1.00 tonne$\cdot$year).
description: 22 pages, 15 figures, 2 tables