Thin scintillation counter with a new readout method for the KOTO experiment

Abstract

Abstract The KOTO experiment at J-PARC is dedicated to the search for the rare decay K L → π 0 ν ν ¯ . While analyzing the data taken in 2018-2018, we found that some background events were caused by K ± decays in the beam. To reduce this background, we are developing a new charged particle detector. It uses a 0.2-mm-thick plastic scintillator. The scintillation light escaping from the surface of the scintillator without total reflection is collected by 12-μm-thick aluminized mylar and is read out by multiple PMTs on the side. Based on the performance evaluated with an electron beam, we expect to have 1/100 K ± background reduction.