Evaluation of Energy Resolution by Changing Angle and Position of Incident Photon in a LYSO Calorimeter

In this paper, we investigate the effect on energy resolution from changing the angle and the position of incidence photon for a 5 $\times$ 5 crystal matrix built with (25 $\times$ 25 $\times$ 200) mm$^{3}$ LYSO scintillating crystals. Those crystals have been proposed for the electromagnetic calorimeter of the Turkish Accelerator Center-Particle Factory (TAC-PF) detector. The energy resolution was obtained as $\sigma_{E}/E = 0.42 \% / \sqrt{E/GeV} \oplus 1.60 \%$ at the center of the matrix in the energy range of 50 MeV to 2 GeV. When we examined the dependence of the energy resolution on the incidence angle of the photon, resolution began to deteriorate at angles greater than $2^{\circ}$ on the 5 $\times$ 5 crystal matrix. Moreover, energy resolution at the corners of the central crystal was worse than at the center of the central crystal by a factor of 1.3 at 50 MeV and 1.1 at 2 GeV.