Lepton flavour universality test at the CERN NA62 experiment

TL;DR

This paper reports a precise measurement of the lepton universality ratio RK at CERN NA62, confirming the Standard Model prediction within experimental uncertainties.

Contribution

The study provides the most precise measurement of RK using a large data sample, testing lepton universality with improved accuracy.

Findings

RK measured as (2.486 +- 0.013) x 10^{-5}

Result consistent with Standard Model

Large data sample enhances measurement precision

Abstract

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.