First measurement of direct CP violation with the NA48 detector at CERN

Abstract

A new advance on direct CP violation in the neutral kaon system has been made by the NA48 Collaboration at CERN. We report on the measurement of the parameter Re(ε'/ε) based on the data collected in 1997. The experiment is performed by studying all four relevant decays modes of K L/K S to π + π − and π 0 π 0 collected simultaneously in the NA48 detector. We have obtained the value Re(ε'/ε)=[18.5±4.5(stat)±5.8(syst)]×10 −4.