A new measurement of direct CP violation in two pion decays of the neutral kaon

Abstract The NA48 experiment at CERN has performed a new measurement of direct CP violation, based on data taken in 1997 by simultaneously collecting K L and K S decays into π 0 π 0 and π + π − . The result for the CP violating parameter Re (e ′ /e) is (18.5±4.5(stat)±5.8(syst))×10 −4 .