1212.4012 (The NA62 collaboration)

Precision Measurement of the Ratio of the Charged Kaon Leptonic Decay
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The NA62 collaboration

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.

View original: http://arxiv.org/abs/1212.4012