In the Belle II experiment we are searching for signals of phenomena related to the so called new physics, based on the B meson, D meson and tau lepton decays. Particle identification, in the whole kinematic range, plays a major role in the reconstruction of decays, especially the efficient separation of kaons and pions. One of the particle identification key systems is the (Aerogel) Ring Imaging Cherenkov Counter, or ARICH. Its working principle is the known relation between the Cherenkov angle (i.e. the angle between particle trajectory and emitted photon direction) and particle velocity. With the detection of Cherenkov photons and subsequent Cherenkov angle reconstruction indirect measurements of particle velocity are performed. Known velocity and momentum measurement information provide means of particle mass determination, based on which particle identity is determined. Simulations and previous studies of sample data have shown the problematic decays of particles, for which a track is measured in the Central Drift Chamber (CDC), but subsequently fail to reach the ARICH detector, on account of scattering phenomena and in-flight decays. In this thesis the enhancement of current methods, based on information provided by other detector system (ECL calorimeter) and the number of Cherenkov photons emitted in the HAPD detector window, will be discussed. Such information is used to construct a probability criteria that is incorporated into the expected detector response calculation (for a given mass hypothesis). On a simulation data sample a major improvement in identification/separation of kaons and pions is subsequently show in the kinematic area below the kaon Cherenkov threshold of <1.5 Gev/c.
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