Study of HQE-PMT property for KamLAND2-Zen

KamLAND2-Zen is an upgrade of the existing KamLAND-Zen, which searchs for neutrino-less double beta decay with 136Xe. 

The update is mainly motivated to improve energy resolution by the combination of brighter LS, HQE-PMT and light collecting mirrors. However, this improvement will make it difficult to measure muon events since the expected number of photo electron will be too large, and non-linear region in PMTs. Increase of after pulse is also serious issue.

In this presentation, we study HQE-PMT property and discuss possible optimization of PMT configuration for KamLAND2-Zen.