Description
The Belle II experiment aims to find physics beyond the standard model using a record size sample of B-Bbar pairs corresponding to the integrated luminosity of 50 1/ab produced in electron – positron collisions at the SuperKEKB accelerator facility in Japan. The Aerogel Ring Imaging CHerenkov counter (ARICH) is the particle identification device installed in the forward end-cap of the Belle II detector. From spring 2019 the fully equipped detector has been stably running, and has mad an important contribution to the interpretation of recorded data. The sample of di–muons events were used for the detector alignment and the measurements of the single photon angular resolution. We measured 14 mrad average angular resolution per photon and 12 photons per Bhabha electron in the 6-8 GeV/c momentum range. To determine the efficiency of the kaon identification and the pion miss-identification probability a sample of charged D* decays with a slow pion in the final state has been used.
