Search for $K^+\to \pi^+ \nu \bar \nu$ at NA62

Flavour physics is one of the most powerful fields for the search of new physics beyond the Standard Model. The kaon sector with the rare decay $K^+\to \pi^+ \nu \bar \nu$ provides one of the cleanest and most promising channels. NA62, a fixed target experiment at the CERN SPS, aims to measure $BR (K^+\to \pi^+ \nu \bar \nu)$ with 10% precision to test the Standard Model validity up to an energy scale of hundreds of TeV. NA62 had dedicated data taking for the $K^+\to \pi^+ \nu \bar \nu$ measurement in 2016 and 2017 and will continue in 2018. Here preliminary results on a fraction of 2016 dataset are presented. The analysis of the complete 2016 data sample is expected to achieve the SM sensitivity.