Measurement of BR(Ke2)/BR(Kμ2) with NA62

The NA62 experiment at CERN SPS collected, during 2007 run, the world largest sample of K±leptonic decays in order to test lepton universality, by measuring the ratio: RK = Γ(K ± → e±ν)/ Γ (K ± → μ±) = γ(Ke2)/ Γ (Kμ2) (1) Being helicity suppressed, due to V-A structure of the charged weak current, RK is sensitive to non-SM effects. The preliminary result of the analysis based on 51089 K± → e ±νcandidates, extracted from a sub-sample of the data set, is: RK = (2.500±0.016) · 10-5, consistent with Standard Model predictions. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.