Search for New Physics in NA62

Abstract

The ratio $R_K=\frac{\Gamma(K\to e \nu_{e} (\gamma))}{\Gamma(K\to \mu \nu_{\mu} (\gamma))}$ of leptonic decay rates provides a golden probe for testing the structure of the weak interactions because it can be predicted with high accuracy within the Standard Model. The aim of the NA62 experimental programme based on the 2007 data set is a measurement of $R_K$ reaching a new accuracy level better than 0.4% \cite{evgueni}. To achieve this goal, data taking strategy allowing control over the systematic effects and in particular precise background subtraction, was worked out, and a data sample of $\sim0.16\times10^6$ $K_{e2}$ candidates with just $\sim10%$ background was collected. The current status of the $K_{l2}$ analysis based on the dedicated NA62 data taking is summarized. The achieved precision of background subtraction, other systematic uncertainties, and prospects of the analysis are discussed. Within the same scientific programme, NA62, in its second phase, will measure the branching ratio of the very rare kaon decay $K^+ \to \pi^+ \nu \overline{\nu}$; the aim is to collect $\mathcal{O}(100)$ events with 10% background in two years data taking period. The status of the project, the R&D and future perspectives for the experiment