Lepton flavour universality and conservation tests in Kaon decays at CERN

摘要

A test of lepton flavour conservation in kaon rare decays by the NA48/2 experiment at CERN SPS is presented. The improved upper limit on the rate of the lepton number violating decay {formula} is established with the data sample collected in 2003-2004. A precision test of lepton flavour universality in kaon rare decays by the successor NA62 experiment at CERN SPS is reported. The helicity suppressed ratio R_K = Γ(K~± → e±~(ν))/Γ(K~(±→μ±)v) is measured with a 0.4% precision using the data sample collected in 2007-2008 and is consistent with the prediction of the Standard Model. The main goal of the NA62 experiment is to measure the branching ratio of the ultra-rare K~(+→) π~+ν{ν under letter -} decay with 10% accuracy. This will be achieved by collecting ~ 10~(13) K~+ decays in the fiducial volume. The NA62 estimated sensitivities to rare and forbidden decays of K~+ and π~0, including lepton flavour and number violating modes, and the NA62 potential to improve on several experimental limits are discussed.