$\mathrm{\cal T}$ -violation and $\mathrm{\cal CPT}$ -invariance measurements in the CPLEAR experiment: a detailed description of the analysis of neutral-kaon decays to $\mathrme \pi \nu$

Abstract

A detailed description of the analysis of neutral kaons decaying to $\mathrme \pi \nu$ is given, based on the complete set of data collected with the CPLEAR experiment. Using a novel approach involving initially strangeness-tagged $\mathrm{K^0}$ and $\mathrm{\overline{K}}{}^0$ , time-dependent decay-rate asymmetries were measured. These asymmetries enabled $\mathrm{\cal T}$ - and $\mathrm{\cal CPT}$ -violation parameters to be measured in the context of a systematic study. The highlights of this study are the first direct observation of $\mathrm{\cal T}$ violation and the direct determination of the $\mathrm{\cal CPT}$ parameter $\mathrm{Re}(\delta)$ with an accuracy improved by two orders of magnitude with respect to the current value.