Methods for Testing theCPTTheorem

Abstract

The decay and interactions of the neutral K mesons are shown to provide some direct tests of the validity of the CPT theorem for weak interactions of strange particles. The connection with related tests of CP and T invariance is also discussed. It is found that the absence of a 2 pi decay mode of the K/sub 2/ is an indication of CP invariance of the nonleptonic interactions of the K meson but not a proof thereof. Even if CPT invariance is assumed, the 2 pi mode does not provide an unambiguous test of CP invariance. It is shown that the absence of a detectable charge asymmetry in the leptonic decay of the K/sub 2/ indicates either CPT or CP invariance of the leptonic interactions if the nonleptonlc interactions sre assumed to be CP invariant. A direct test of CP invariance would be provided by a measurement of the interference term in the leptonic decay curve of the K/sup 0/ as noted by Sachs and Treiman. A direct test of CPT invariance would be provided by an accurate measurement of the interference term for each of the charge states in the leptonic decay of the K/ sup 0/. It ismore » shown that a specific test of combined CPT and CP invariance of the weak interactions would be provided by a measurement of the elastic and regenerative scattering of K/sub 1/ and K/sub 2/ mesons by nuclei. The value of the K/sub 1/-K/sub 2/ mass difference determined by the interference method is found to be independent of the question of CPT or CP invariance. On the other hand the evidence for DELTA S = - DELTA Q transitions obtained from the ratio of the leptonic decay rates of K/sub 1/ and K/sub 2/ mesons does depend on the assumption of either CPT or CP invariance of the nonleptonic interactions. This ambiguity can be removed by an accurate determination of the charge asymmetry in the leptonic decays. (auth)« less