Measurement of the charge asymmetry for the K_S → πeν decay and test of CPT symmetry with the KLOE detector

Using 1.63 fb⁻¹ of integrated luminosity collected by the KLOE experiment about 7 × 10⁴K_S → π^±e^∓ν decays have been reconstructed. The measured value of the charge asymmetry for this decay is A_S = (−4.9 ± 5.7_stat ± 2.6_syst) × 10⁻³, which is almost twice more precise than the previous KLOE result. The combination of these two measurements gives A_S = (−3.8 ± 5.0_stat ± 2.6_syst) × 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.