Reduction of neutron-induced background in KOTO

10th International Conference on Kaon Physics

Nakagiri, Kota^1

Department of Physics, Faculty of Science, Kyoto University Kitashirakawa, Oiwake-cho, Sakyo-ku, Kyoto

606-8502, Japan^1

关键词: Analysis of data;    Electromagnetic calorimeter;    Hadronic showers;    Photon discrimination;    Secondary neutrons;    Two photon;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/800/1/012025/pdf
DOI  :  10.1088/1742-6596/800/1/012025

来源: IOP

【 摘 要 】

The KOTO experiment aims to study the KL→ π0v v decay at J-PARC. In order to identify the signal, we measure two photons from a π0decay with an electromagnetic calorimeter consisting of undoped CsI crystals, and ensure that there are no other particles with hermetic veto counters. In the analysis of data taken in 2013, the neutron-induced background, which was caused by a beam-halo neutron hitting the calorimeter was dominant. The neutron makes a primary hadronic shower and a secondary neutron emitted from the shower makes a secondary shower after traveling inside the calorimeter. If these two shower clusters are observed in the calorimeter without any hits in veto detectors, it can mimic a signal event. We developed new methods to suppress this background, such as neutron-photon discrimination methods using cluster shape and pulse shape. We obtained (3:8+2:4-1:1) × 104reduction power for the neutron- induced background.