Direct tests of T, CP, CPT symmetries in transitions of neutral K mesons with the KLOE experiment

TL;DR

This paper reports on direct tests of T, CP, and CPT symmetries in neutral kaon transitions using entangled pairs from the KLOE experiment, achieving high-precision results and observing CP violation through novel time-dependent analysis.

Contribution

It introduces a new method for testing T, CP, and CPT symmetries in kaon transitions using entangled kaon pairs and time difference distributions, providing the first such tests with few percent precision.

Findings

First-time T and CPT symmetry tests in kaon transitions with high precision.

Observation of CP violation using a novel time-dependent approach.

Consistent results with the Standard Model predictions.

Abstract

Tests of the T, CP and CPT symmetries in the neutral kaon system are performed by the direct comparison of the probabilities of a kaon transition process to its symmetry-conjugate. The exchange of in and out states required for a genuine test involving an anti-unitary transformation implied by time-reversal is implemented exploiting the entanglement of $K^0\bar{K}{}^0$ pairs produced at a $\phi$-factory. A data sample collected by the KLOE experiment at DA$\Phi$NE corresponding to an integrated luminosity of about 1.7 fb$^{-1}$ is analysed to study the $\Delta$t distributions of the $\phi\to K_{S}K_{L}\to \pi^+\pi^- \: \pi^{\pm}e^{\mp}\nu$ and $\phi\to K_{S}K_{L}\to \pi^{\pm}e^{\mp}\nu \: 3\pi^0$ processes, with $\Delta$t the difference of the kaon decay times. A comparison of the measured $\Delta$t distributions in the asymptotic region $\Delta t \gg \tau_{S}$ allows to test for the first time T and CPT symmetries in kaon transitions with a precision of few percent, and to observe CP violation with this novel method.