Direct CP Violation in Charged Kaon Decays by the NA48/2 Experiment at CERN

Abstract

The NA48/2 experiment at CERN is performing high precision studies of charged kaon decays, using an upgraded NA48 setup and a novel design for simultaneous unseparated K ± beams. The main goal is to search for direct CP violation in decays to three pions with a sensitivity at a level of 10 −4 on the asymmetry A g = ( g + − g − ) / ( g + + g − ) where g is the linear slope parameter in the Dalitz plot. The experimental procedure and the main systematic effects are discussed, based on the preliminary analysis of a fraction (less than 50%) of the data recorded. The statistical errors on the K ± → π + π − π ± and K ± → π 0 π 0 π ± asymmetries are 2.7 × 10 −4 and 5 × 10 −4 , respectively. The large amount of charged kaon decays collected allow also precision measurements of several rare decay processes.