NA62 is a fixed-target experiment at the CERN SPS dedicated to measurements of rare kaon decays. Such measurements, like the branching fraction of the K+ → π+ ν ν̄ decay, have the potential to bring significant insights into new physics processes when comparison is made with precise theoretical predictions. For this purpose, innovative techniques have been developed, in particular, in the domain of low-mass tracking devices. Detector construction spanned several years from 2009 to 2014. The collaboration started detector commissioning in 2014 and will collect data until the end of 2018. The beam line and detector components are described together with their early performance obtained from 2014 and 2015 data.

A precision measurement of the ratio RKRK of the rates of kaon leptonic decays K±→e±νK±→e±ν and K±→μ±νK±→μ±ν with the full data sample collected by the NA62 experiment at CERN in 2007–2008 is reported. The result, obtained by analysing View the MathML source∼150000 reconstructed K±→e±νK±→e±ν candidates with 11% background contamination, is RK=(2.488±0.010)×10−5RK=(2.488±0.010)×10−5, in agreement with the Standard Model expectation

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