Precise measurement of B(K\to e\nu(\gamma))/B(K\to \mu\nu(\gamma)) and study of K\to e\nu\gamma

TL;DR

This paper reports a precise measurement of the ratio of decay rates of kaons into electrons versus muons, studies the radiative decay process, and compares results with Standard Model predictions to constrain new physics models.

Contribution

It provides the most precise measurement of R_K and detailed analysis of K→eνγ decay, improving constraints on lepton flavor violation in the MSSM.

Findings

Measured R_K = (2.493±0.025±0.019)×10^{-5}

Confirmed agreement with Standard Model expectations

Analyzed the differential decay rate for K→eνγ

Abstract

We present a precise measurement of the ratio R_K=B(K\to e\nu(\gamma))/B(K\to \mu\nu(\gamma)) and a study of the radiative process $K\to e\nu\gamma$, performed with the KLOE detector. The results are based on data collected at the Frascati $e^+e^-$ collider DAFNE for an integrated luminosity of 2.2 fb$^{-1}$. We find R_K = (2.493\pm0.025\pm0.019)x10^{-5}$, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation. We also measured the differential decay rate $d\Gamma(K\to e\nu\gamma)/dE_\gamma$ for photon energies $10<E_\gamma<250$ MeV. Results are compared with predictions from theory.