Recent results on Direct CP Violation and charged kaon decays with the NA48/2 experiment

The CP violation played an important role in the understanding of the intimate nature of the weak interaction from the early times of particle physics. After more than three decades since the discover of CP violation in the neutral kaons by Christenson, Cronin, Fitch and Turlay [1] a new kind of CP violation, the so called Direct CP violation that happens directly in the decay, was definitively discovered. After the unconfirmed indication by NA31 [2], KTev [3] and NA48 [4] have demonstrated, with high significance, that direct CP violation exists in the decays of neutral kaons into two pions (only recently the direct CP violation has been found also in the B sector [5]). However the deep understanding of the CP violation is still an important tool both in the test of Standard Model (SM) and in the discovery of the physics beyond the SM. Indeed a possible non-SM structure could appear in the heavy quarks loops which are responsible of the direct CP violating processes. Besides the already measured quantity ε /ε , the most promising observables are the charge asymmetry in the K → 3π decay and the decay rates of the GIM suppressed decays. The main goal of the NA48/2 experiment is to measure the charge asymmetry in the 3π mode of the charged kaons with a statistical precision of ∼ 10−4 and a smaller systematic error, both in K± → π±π+π− and in K± → π±π0π0 . A novel design for the beam line and an upgrade of the NA48 detector are adopted to allow the simultaneous detection of decays from K+/Kunseparated beams. After a brief description of the beam line and detector, the analysis technique and the main systematics will be discussed to present the preliminary result in the charged mode: