Evaluation of particle identification performance in the Belle II experiment with the first collision data

The Belle experiment - an electron-positron collider B factory experiment - discovered new hadrons, such as exotic states and charmed baryons. The upgraded Belle II experiment has started taking collision data in April 2018. We are going to take a factor of 50 more data than the Belle experiment, thanks to the increase in the instantaneous luminosity. The much larger dataset will increase the capability to discover new hadrons and precisely measure their properties. In these studies, the identification of charged pions, kaons, and protons is essential to reduce massive backgrounds.

The Belle II experiment introduced new Particle Identification (PID) detectors based on Ring Imaging Cherenkov technologies: a Time Of Propagation counter and an Aerogel-RICH counter. These detectors provide us with higher PID performance, which we have to understand in detail. 

In this work, PID performance was evaluated using  D^*+ and Λ decays, which provide high-purity pion, kaon, and proton samples and can be selected without using PID information. An overview of the performance for the individual sub-detectors and for the combination of all the sub-detectors using the first collision data will be presented.