Tests of the discrete symmetriesC,P, andTin one-photon transitions of positronium

Abstract

We examine one-photon transitions in positronium (Ps) as possible tests of the discrete symmetries of C (charge-conjugation) and/or P (parity) and/or T (time-reversal) invariance. We discuss two general classes of experiment. The first class consists of direct searches for transitions forbidden by a given symmetry. The second class is composed of experiments that search for an asymmetry in the rate of an allowed transition upon reversal of an externally controllable vector quantity, such as an applied magnetic field B or rf photon spin ${\mathrm{S}}_{\gamma }$. For a given symmetry, we compare limits on symmetry-violating mixings, which can reasonably be expected from these Ps experiments, with limits placed by existing atomic experiments. We conclude from this analysis, that the most promising experiments in Ps are those that search for C violation with no P violation.