Search for the rare decay KL→π0νν¯ at J-PARC KOTO experiment
Shuichi Shinohara
Abstract
Abstract The KOTO experiment aims to study the CP-violating rare decay <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>K</mml:mi> <mml:mi>L</mml:mi> </mml:msub> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>π</mml:mi> <mml:mn>0</mml:mn> </mml:msup> <mml:mi>ν</mml:mi> <mml:mover accent="true"> <mml:mi>ν</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:mrow> </mml:math> at J-PARC. The analysis of the data set taken in 2016, 2017 and 2018 is reported. In order to reduce backgrounds and to improve the signal acceptance, a new barrel photon detector and a new trigger system were installed and new analysis techniques were developed. The K L yield was 7.1×10 12 . The single event sensitivity was estimated to be 6.9×10 −10 , which was improved by a factor of 2 compared to the data set taken in 2015. The number of background events was estimated to be 0.05 ± 0.02. Four candidate events were observed in the signal region, and their studies are on-going extensively to nd their sources.