Probing the lepton universality with K±l2 decays

The ratio of the decay rates RK=Γ(K±→e±ν)/Γ(K±→μ±ν) provides a powerful probe for the weak interaction structure. Recent calculations show its sensitivity to possible presence of New Physics. The value of RK is calculated with very high precision within the Standard Model, however the achieved accuracy by the previous experiments is two orders of magnitude lower due to the lack of statistics. During two years of data taking at the CERN SPS accelerator, the NA48/2 experiment has collected more than four times the World statistics sample of K±→e±ν decays allowing to perform a precision measurement of the ratio RK and to test the theoretical predictions. The preliminary result RK=(2.416±0.043stat±0.024syst)×10−5 is presented.