Lepton universality test with Kl2 decays at NA62 experiment

TL;DR

The NA62 experiment at CERN measured the ratio of leptonic kaon decays to test lepton universality, finding results consistent with the Standard Model predictions.

Contribution

This work provides a precise measurement of the lepton universality ratio R_K using a large sample of K+ decays at CERN.

Findings

Measured R_K = (2.500 ± 0.016) x 10^{-5}

Result consistent with Standard Model predictions

Large data sample improves precision of lepton universality tests

Abstract

The experiment NA62 at CERN collected a large sample of K+- leptonic decays in order to perform precise test of lepton universality, by measuring the helicity suppressed ratio R_K=Gamma(K+- --> e+- nu)/Gamma(K+- --> mu+- nu). The preliminary result of the analysis based on 51089 K+ --> e+nu candidates is R_K=(2.500+-0.016)x10^{-5}, consistent with the predictions of the Standard Model.