Search for direct CP-violation in K+- --> pi+-pi0pi0 decays

TL;DR

This paper reports a highly precise search for direct CP-violation in K+- --> pi+-pi0pi0 decays, using a large dataset from the NA48/2 experiment, finding no significant asymmetry and improving measurement precision.

Contribution

It presents the most precise measurement to date of the CP-violation asymmetry in K+- --> pi+-pi0pi0 decays, with improved control of instrumental effects.

Findings

Measured asymmetry A_g = (1.8 ± 2.6) x 10^{-4}

Result is consistent with no CP-violation

Significantly improved the precision over previous experiments

Abstract

A search for direct CP-violation in K+- --> pi+-pi0pi0 decays based on 47.14 million events has been performed by the NA48/2 experiment at the CERN SPS. The asymmetry in the Dalitz plot linear slopes A_g=(g^+ - g^-)/(g^+ + g^-) is measured to be A_g=(1.8 +- 2.6).10^{-4}. The design of the experiment and the method of analysis provide good control of instrumental charge asymmetries in this measurement. The precision of the result is limited by statistics and is almost one order of magnitude better than that of previous measurements by other experiments.