Design of a Electromagnetic Calorimeter Trigger System for the Belle II Experiment

Abstract

The Belle II experiment is currently being constructed at the KEK High Energy Accelerator Research Organization in Japan to probe the New Physics phenomena from mainly rare B and D mesons, and tau lepton weak decays with the ultimate goal of an integrated luminosity of 50 ab(-1). If beam backgrounds are to be reduced and physics events are to be enhanced during data. acquisition, a trigger system is indispensable. For this purpose, we have designed a Belle II calorimeter trigger system to generate total energy, cluster counting and Bhabha triggers that are crucial for smooth operation of the experiment. We have also measured the noise level of a trigger cell composed of 16 CsI(Tl) crystal counters at a level of 10 MeV and estimated the trigger timing latency to be 3 mu s, which satisfies the requirement of global online trigger latency for the experiment.