Eur. Phys. J. C (2009) 64: 627-636
https://doi.org/10.1140/epjc/s10052-009-1177-x

Regular Article - Experimental Physics

Precise measurement of Γ(K→e ν(γ))/Γ(K→μ ν(γ)) and study of K→e ν γ

¹ Laboratori Nazionali di Frascati dell’INFN, Frascati, Italy
² Institut für Kernphysik, Johannes Gutenberg-Universität, Mainz, Germany
³ Dipartimento di Scienze Fisiche dell’Università “Federico II”, Napoli, Italy
⁴ INFN Sezione di Napoli, Napoli, Italy
⁵ Dipartimento di Energetica dell’Università “La Sapienza”, Rome, Italy
⁶ Dipartimento di Fisica dell’Università “La Sapienza”, Rome, Italy
⁷ INFN Sezione di Roma, Rome, Italy
⁸ Dipartimento di Fisica dell’Università “Tor Vergata”, Rome, Italy
⁹ INFN Sezione di Roma Tor Vergata, Rome, Italy
¹⁰ Dipartimento di Fisica dell’Università “Roma Tre”, Rome, Italy
¹¹ INFN Sezione di Roma Tre, Rome, Italy
¹² Physics Department, State University of New York, Stony Brook, USA
¹³ Institute for Theoretical and Experimental Physics, Moscow, Russia

^* e-mail: Mario.Antonelli@lnf.infn.it

Received: 21 July 2009
Revised: 14 September 2009
Published online: 28 October 2009

Abstract

We present a precise measurement of the ratio R _K =Γ(K→e ν(γ))/Γ(K→μ ν(γ)) and a study of the radiative process K→e ν γ, performed with the KLOE detector. The results are based on data collected at the Frascati e ⁺ e ⁻ collider DAΦNE for an integrated luminosity of 2.2 fb⁻¹. We find R _K =(2.493±0.025_stat±0.019_syst)×10⁻⁵, 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 dΓ(K→e ν γ)/dE _γ for photon energies 10<E _γ < 250 MeV. Results are compared with predictions from theory.