In-flight Search for K+→π+νν¯: First NA62 Results

In this paper the prospects to make a precise measurement of the K+→π+νν ̅ decay using a new kaon decay in-flight technique are reviewed. A preliminary result based on data collected in 2016 yielded one candidate event, compatible with the Standard Model prediction. Assuming that the event is background, an upper limit of 1.4×10−9 (95% CL) has been placed. NA62 is currently taking data: it is expected that with the full data sample recorded before the CERN long shutdown 2 (LS2), the experiment will have about 20 SM events