The K+ to pi+ nu nubar decay has been attracting interest for many decades. The accurate measurement of its branching ratio is a powerful test of the Standard Model (SM) and could reveal effects beyond the SM. As the decay occurs at the level of 1 in 10 billion kaon disintegration, many experimental challenges have to be overcome.
The CERN NA62 experiment uses a novel kaon decay-in-flight technique to observe K+ to pi+ nu nubar. The analysis of the 2016 data set was used to establish the method by allowing us to reach the 10^-10 single event sensitivity. The preliminary NA62 result on K+ to pi+ nu nubar from the analysis of the full 2016 data set will be presented.