Measurement of BR(Ke2)/BR(Kμ2) in the NA62 experiment at CERN

The Measurement of the helicity suppressed ratio of charged kaon leptonic decay rates RK = Γ (K± → e±νe)/Γ(K± → μ±νμ) has long been considered as an excellent test of lepton universality and the Standard Model (SM) description of weak interactions. It was realized recently that the suppression of the SM contribution might enhance the sensitivity to SUSY-induced effects to an experimentally accessible level. The NA62 experiment at the CERN SPS has collected over 105 K → e ν decays during a dedicated run in 2007, aiming at achieving 0.5 % precision. Experimental strategy, details of the analysis and the final result on a partial set of data will be described. The result RK = (2.487 ± 0.013) × 10−5 is in agreement with the Standard Model expectation.