Precision Measurements with Kaons at CERN

The NA62 experiment at CERN took data in 2016-2018 with the main goal of measuring the K+ -> pi(+)v (v) over bar. decay. The high-intensity fixed-target setup and the detector performance make the NA62 experiment particularly suited to make precision measurements of charged kaon decays. Preliminary results of the K-+/- -> pi(0)pi(0)mu(+/-)upsilon(K-mu 4(00)) decay first observation and analysis based on NA48/2 data collected in 2003-2004 are presented. Results from studies of K+ ->pi(0)e+vy(K-e3(0)) decays are reported, based on a data sample of more than 10(5) K-0 (e3) candidates recorded in 2017-2018. Preliminary results with the most precise measurements of the K-0 (e3) branching ratios and of T-asymmetry in the K0 e3 decay are presented. The flavourchanging neutral current decay K+ -> pi(+) mu(+) mu(-) is induced at the one-loop level in the Standard Model. Preliminary results from an analysis of the K+ -> pi(+) mu(+) mu(-) decay are reported, using a large sample of about 3x10(12) kaon decays into two muons recorded with a downscaled dimuon trigger operating along with the main trigger. The most precise determination of the K+ -> pi(+) mu(+) mu(-) form-factor parameters alpha(+) and b(+) has been made by NA62 using data collected in 2017 and 2018.