Violation of time-reversal invariance and CPLEAR measurements

Motivated by the recent CPLEAR measurement on the time-reversal non-invaria nce, we review the situation concerning the experimental measurements of ch arge conjugation, parity violation and time reversibility, in systems with non-Hermitean Hamiltonians. This includes in particular neutral meson syste ms, like K-0 - (K) over bar(0), D-0 - (D) over bar(0) and B-0 - (B) over ba r(0). We discuss the formalism that describes particle-antiparticle mixing and time evolution of states, paying particular emphasis to the orthogonali ty conditions of incoming and outgoing states. As a result, we confirm that the CPLEAR experiment makes a direct measurement of violation of time-reve rsal without any assumption of unitarity and CPT-violation. The asymmetry w hich signifies T-violation, is found to be independent of time and decay pr ocesses. (C) 1999 Published by Elsevier Science B.V. All rights reserved.