Test of Lepton Flavour Universality in K+ --> l+nu Decays

TL;DR

This paper reports a precise measurement of the ratio of kaon decay rates to electrons and muons, testing lepton flavour universality and confirming Standard Model predictions.

Contribution

The study provides a high-precision experimental test of lepton flavour universality in kaon decays, with results consistent with the Standard Model.

Findings

Measured RK = (2.487 ± 0.013) × 10^{-5}

Results agree with Standard Model predictions

Sample of 59813 reconstructed decays

Abstract

A precision test of lepton flavour universality has been performed by measuring the ratio RK of kaon leptonic decay rates K+ --> e+nu and K+ --> mu+nu in a sample of 59813 reconstructed K+ --> e+nu candidates with (8.71 +- 0.24)% background contamination. The result RK = (2.487 +- 0.013) * 10^{-5} is in agreement with the Standard Model expectation.