Construction and performance of 4-D CsI calorimeter for the $K_L\to \pi^0 \nu \bar{\nu}$ search of KOTO experiment

Katsushige Kotera, KOTO collaboration
2021 Proceedings of 40th International Conference on High Energy physics — PoS(ICHEP2020)   unpublished
A major background for the → 0¯s earch at the KOTO experiment is caused by neutrons generating two showers in the calorimeter made of 50 cm-long 2760 undoped CsI crystals stacked in a 1.9 m-diameter cylinder. Neutrons tend to have interactions deeper than photons. In 2018 we upgraded the calorimeter by installing 4080 silicon photomultipliers (SiPMs) on the front surface. Each crystal has been read out with a PMT on the back surface of the crystal. The depth and timing information on each
more » ... ation on each shower are obtained by measuring the difference and the average of the timing of SiPM and PMT. A clear separation of gamma-and neutron-events was achieved in 2019 data. Less than 0.3 neutron background events are expected when we reach the Standard-Model sensitivity of →
doi:10.22323/1.390.0749 fatcat:xwopmlt26nernop5tnkldy7y4u