Measurement of the charge asymmetry for the Ks → πeν decay and test of CPT symmetry with the Kloe detector

Abstract

Studies presented in this paper were conducted using 1.63 fb−1 of integrated luminosity collected by the KLOE experiment. The excellent time resolution of the electromagnetic calorimeter and the very good accuracy on both momentum and vertex reconstruction of the tracking system allow to reconstruct about 7 × 104 KS → π±e∓ν decays. The measured value of the charge asymmetry for this decay is AS = (−4.9±5.7stat±2.6syst)×10−3, which is almost twice more precise than the previous KLOE result. The combination of these two measurements gives AS = (−3.8 ± 5.0stat ± 2.6syst) × 10−3 and, together with the asymmetry of the KL semileptonic decay, provides significant tests of the CPT symmetry. The obtained results are in agreement with CPT invariance.