Precision Tests of Fundamental Interactions

Search for K+→ π+ν¯ν at NA62

Search for K+→ π+ν¯ν at NA62: Recently, NA62 (in talks at conferences, and soon to be published) announced its first results based on a small initial data set, with the observation of one event compatible with K+→ π+ν¯ν decay.  An upper limit on the branching ratio of <14x the SM expectation was set demonstrating that the experiment basically works a planned (after 10 years of development). Since data with about 30x the sensitivity has been already acquired, the experiment is on track to meet its goals of improving the measurement sensitivity by an order of magnitude compared the work done at BNL where K+→ π+ν¯ν was initially discovered with a few events observed at the one in 10 billion level. The precise measurement of this tiny branching ratio will severely test the predictions of the SM and reveal or limit the prospects for certain new avenues of theoretical speculation which go beyond the SM.