Study on Reactor Neutrino Directionality Search Utilizing Vertex Information Reconstructed by PMT Operating State in a Liquid Scintillator Detector

The properties of neutrinos are not well known because they weakly interact with surrounding matter. Recently, several interesting results and phenomena have been measured using reactor neutrinos. Although there are various types of detectors that detect neutrino signals, they generally use photomultiplier tubes (PMTs) to collect data. In particular, signals obtained from each PMT surrounding a detector are used to reconstruct a vertex of an incident neutrino in the detector. However, if a number of PMTs are out of operation from the initial installation, the performance of the PMT or its operation efficiency may be changed over time. This may affect the information for the reconstructed vertex of an incident neutrino, which can have a direct impact on results that utilize the reconstructed vertex information. This article briefly describes the change of reconstructed vertex according to operating status of PMTs around the reactor neutrino detector by using a Monte Carlo (MC) simulation based on a cylindrical detector equipped with liquid scintillator. The MC simulation for this analysis needs a moderate number of central processing units (CPUs) and cores. Therefore, various resources and servers at a supercomputing center were used. Our results can be used to more accurately conduct research related to neutrino direction using PMT information in the future.