Precision Measurement of the Ratio of the Charged Kaon Leptonic Decay Rates
arXiv:1212.4012
Abstract
A precision measurement of the ratio RK of the rates of kaon leptonic decays K+- --> e nu and K+- --> mu nu with the full data sample collected by the NA62 experiment at CERN in 2007-2008 is reported. The result, obtained by analysing ~150000 reconstructed K+- --> e nu candidates with 11% background contamination, is RK = (2.488+-0.010)*10^{-5}, in agreement with the Standard Model expectation.
Accepted for publication in Physics Letters B (18 January 2013). 18 pages, 6 figures