Measurement of the charge asymmetry for the $K_S \rightarrow \pi e \nu$ decay and test of CPT symmetry with the KLOE detector

TL;DR

This paper reports a precise measurement of the charge asymmetry in $K_S$ decays to test CPT symmetry, finding results consistent with CPT invariance using data from the KLOE detector.

Contribution

It provides the most precise measurement to date of the $K_S$ charge asymmetry and tests CPT symmetry with improved accuracy.

Findings

Measured $A_S$ with nearly twice the precision of previous results.

Combined asymmetry results are consistent with CPT invariance.

Supports the validity of CPT symmetry within experimental uncertainties.

Abstract

Using 1.63 fb$^{-1}$ of integrated luminosity collected by the KLOE experiment about $7\times 10^4$ $K_S \rightarrow \pi^{\pm}e^{\mp}\nu$ decays have been reconstructed. The measured value of the charge asymmetry for this decay is $A_S = (-4.9 \pm 5.7_{stat} \pm 2.6_{syst}) \times 10^{-3}$, which is almost twice more precise than the previous KLOE result. The combination of these two measurements gives $A_S = (-3.8 \pm 5.0_{stat} \pm 2.6_{syst}) \times 10^{-3}$ and, together with the asymmetry of the $K_L$ semileptonic decay, provides significant tests of the CPT symmetry. The obtained results are in agreement with CPT invariance.