Precision test of the SM with Kl2 and Kl3 decays at KLOE

TL;DR

This paper reports precision measurements of kaon decays at KLOE to test the Standard Model's unitarity and search for new physics, including lepton-flavor violation and charged Higgs contributions.

Contribution

It provides new high-precision measurements of Kl3 decay widths and the R_K ratio, offering constraints on new physics models beyond the Standard Model.

Findings

Constraints on new physics models from Kl3 decay measurements

A new measurement of R_K with % level accuracy

No significant deviation from SM predictions observed

Abstract

Kaon decay studies seeking new-physics (NP) effects in leptonic (K_l2) or semileptonic (K_l3) decays are discussed. A unitarity test of the first row of the CKM mixing matrix is obtained from the KLOE precision measurements of Kl3 widths for K^+-, K_L, and (unique to KLOE) K_S, complemented with the absolute branching ratio for the K_mu2 decay. KLOE results lead to constraints for NP models and can probe possible charged Higgs exchange contribution in SM extensions with two Higgs doublets. The main focus in the present document is set on a new measurement of R_K=Gamma(K_e2)/Gamma(K_mu2) with an accuracy at the % level, aiming at finding evidence of deviations from the SM prediction induced by lepton-flavor violation NP effects.