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A precision lepton universality test by measurement of the helicity suppressed ratio of leptonic decay rates of the charged kaon with ∼ 150000 K ± → e ± ν decays collected by the NA62 experiment in 2007-08 is presented. The record accuracy of 0.4% constrains the parameter space of new physics models with extended Higgs sector, a fourth generation of quarks and leptons or sterile neutrinos. An improved upper limit on the rate of the lepton number violating decay K ± → π ∓ μ ± μ ± , which probesdoi:10.1051/epjconf/20149503029 fatcat:krcssc4ssrf4rk2brq2hlvxtxq