JUNO is designed to determine the neutrino mass ordering with an energy resolution of 3% at 1 MeV. In the real detector, however, deformations of the central stainless-steel structure during installation lead to deviations of the photomultiplier tube (PMT) positions from their design values. Based on the limited survey data of the PMTs and the stainless-steel truss, we perform a correlation analysis of the measured points and propose a method to predict the positions of all PMTs. Using the resulting realistic geometry, we demonstrate that the detector deformation has a negligible effect on the energy reconstruction. In contrast, inaccuracies in the assumed geometry can introduce vertex biases of up to 40 mm. Incorporating the realistic geometry into the calibration-based PMT response model removes this bias and preserves the stability of the reconstruction algorithms.
@article{arxiv.2604.13747,
title = {Realistic Detector Geometry Modeling and Its Impact on Event Reconstruction in JUNO},
author = {Zhaoxiang Wu and Miao He and Wuming Luo and Ziyan Deng and Wei He and Yuekun Heng and Xiaoping Jing and Bo Li and Xiaoyan Ma and Xiaohui Qian and Zhonghua Qin and Yifang Wang and Peidong Yu},
journal= {arXiv preprint arXiv:2604.13747},
year = {2026}
}