Monte Carlo Modelling of the CP Violation Search in Positronium (CPVPS) Experiment

Combined Charge conjugation and Parity symmetry (CP) violation is a necessary ingredient to explain the matter—anti-matter asymmetry in the universe. However, the amount of CP violation observed in experiments up to now is not enough to account for the imbalance. We are investigating potential CP violation in the three-photon decay of tensor polarized ortho-positronium (o-Ps). Our experiment uses an array of gamma detectors composed of silicon photomultipliers coupled to LYSO scintillation crystals in a superconducting magnet. Our setup includes 48 gamma ray detectors in the magnet bore with a positron source at the center, held in place by support structures . Positrons from the source travel through a start detector and deposit some of their energy. The positrons then enter a region where Ps is formed and decays. We use EGSnrc to perform Monte Carlo simulations of particle transport in this setup. With EGSnrc, we analyze unwanted decay modes, such as the two 511 keV gamma rays from para-positronium annihilation, scattering, and LYSO's intrinsic radiation, to quantify background levels. I will present on the simulations of background radiation and quantifying it.