Recent CP violation and |Vus| measurements from the NA48 experiment

Over the last decade the NA48 collaboration at CERN has carried out an extensive experimental program dedicated to study CP violation (CPV) and rare processes in both neutral and charged kaon decays. A selection of results from recent analysis is compared with other measurements and theoretical predictions to provide constraints on CPV and on the CKM matrix. The observable +is related to the parameters of indirect and direct CPV (+= + ’) and is defined as the CP violating amplitude ratio of the neutral kaon decaying into two charged pions, += A(KL ) / A(KS ). NA48 has determined | +| by measuring the ratio of decay rates (KL )/(KLe). We obtain | +| = (2.223 ± 0.012)10 . The main objective of NA48/2 has been to search for direct CPV by high precision measurement of the asymmetry Ag= (g + g) / (g + g) of the linear slope parameter g in the Dalitz plot of K3 decays. NA48/2 used simultaneous K/K beams which allow a high level of control of systematic effects. From the large data sample (3 10 K and 9 10 K) we obtained the final results Ag = (-1.5 ± 2.1) 10 -4 and Ag = (1.8 ± 1.8) 10 -4 compatible with SM predictions. These results correspond to more than one order of magnitude improvement in precision with respect to previous measurements and are limited by the statistics of the data sample. The decay rates R(Ke3/K2), R(K3/K2) and R(K3/Ke3) have been measured with charged K decays from special data samples with a low bias trigger in the NA48/2 experiment. Using the latest result for the K normalization channel, the Ke3 and  branching fractions are then used as input to deduce the CKM matrix element VUS.