Investigations of fundamental symmetries with the electron-positron systems

Abstract

This work concerned two experimental searches for the violation of fundamental discrete symmetries in physical systems originating from electron-positron interactions. The first study was a direct test of the symmetry under reversal in time in transitions of neutral K mesons, performed with quantum-entangled neutral kaon pairs. Data collected by the KLOE experiment operating at the DAFNE collider in 2004-2005 were studied to select events of the KsKl->pi e nu 3pi0 and KsKl->pi+pi- pi e nu processes and compare their rates. Rates of each process identified by two time-ordered neutral kaon decays, determined as a function of a difference between kaon decays, were used to measure the asymptotic level of two T-violation sensitive ratios of double kaon decay rates, yielding the values of R2=1.020+/-0.017stat+/-0.035syst and R4=0.990+/-0.017stat+/-0.039syst. Although these results do not reach the sensitivity needed to probe T violation, this measurement proves the required reconstruction and analysis of the data is feasible and prospects exist for a statistically significant T test with a larger dataset collected by the KLOE-2 experiment if certain systematic effects are eliminated. The second part of this work comprised a demonstration of feasibility of using the J-PET detector to search for non-vanishing angular correlations in the decays of ortho-positronium atoms. Feasibility of identification of 3gamma events as well as reconstruction of their origin points using a dedicated trilateration-based method was demonstrated using MC simulations and a test measurement performed with the J-PET detector.