Lepton flavour universality test at the CERN NA62 experiment

A precision test of lepton universality by measurement of the ratio RK of K-->e nu to K-->mu nu decay rates was performed using a sample of 59963 K-->e nu candidates with 8.8% background contamination collected by the CERN NA62 experiment. The result RK = (2.486 +- 0.013)*10^{-5} is in agreement with the Standard Model expectation.