Pion radiative weak decays in nonlocal chiral quark models

TL;DR

This paper investigates the radiative decay of pions using nonlocal chiral quark models with wave function renormalization, calculating form factors and slopes that align well with experimental data.

Contribution

It introduces calculations of vector and axial-vector form factors in nonlocal chiral quark models, including wave function renormalization, and compares results with experimental data and other models.

Findings

Calculated FV and FA form factors at q^2=0 agree with experiments.

Determined the slope a of FV(q^2) at q^2 -> 0 consistent with data.

Showed nonlocal form factors from lattice QCD improve model predictions.

Abstract

We analyze the radiative pion decay pi+ -> e+ nu_e gamma within nonlocal chiral quark models that include wave function renormalization. In this framework we calculate the vector and axial-vector form factors FV and FA at q^2=0 --where q^2 is the (e+ \nu_e) squared invariant mass-- and the slope a of FV(q^2) at q^2 -> 0. The calculations are carried out considering different nonlocal form factors, in particular those taken from lattice QCD evaluations, showing a reasonable agreement with the corresponding experimental data. The comparison of our results with those obtained in the (local) NJL model and the relation of FV and a with the form factor in pi^0 -> gamma* gamma decays are discussed.