title: Two-loop effective theory analysis of pi (K)-->enu[over ]_{e}[gamma] branching ratios.
abstract: We study the ratios R_{e/mu};{(P)} identical withGamma(P-->enu[over ]_{e}[gamma])/Gamma(P-->munu[over ]_{mu}[gamma]) (P=pi, K) in Chiral Perturbation Theory to order e;{2}p;{4}. We complement the two-loop effective theory results with a matching calculation of the counterterm, finding R_{e/mu};{(pi)}=(1.2352+/-0.0001)x10;{-4} and R_{e/mu};{(K)}=(2.477+/-0.001)x10;{-5}.
authors.affiliation: Theoretical Division, Los Alamos National Laboratory, Los Alamos New Mexico 87544, USA.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Cirigliano
authors.forename: Ignasi
authors.initials: I
authors.lastname: Rosell