Lepton flavour universality and conservation tests in Kaon decays at CERN

Abstract

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 K±→ π ?μ±μ± 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 RK = Γ(K± → e±ν)/Γ(K± → μ±ν) 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+νν decay with 10% accuracy. This will be achieved by collecting ∼ 1013K+ decays in the fiducial volume. The NA62 estimated sensitivities to rare and forbidden decays of K+ and π0, including lepton flavour and number violating modes, and the NA62 potential to improve on several experimental limits are discussed. © Owned by the authors, published by EDP Sciences, 2014.