First lattice calculation of radiative leptonic decay rates of pseudoscalar mesons

We present a nonperturbative lattice calculation of the form factors which contribute to the amplitudes for the radiative decays P -> l (v) over bar (l gamma), where P is a pseudoscalar meson and l is a charged lepton. Together with the nonperturbative determination of the corrections to the processes P -> l (v) over bar (l),= due to the exchange of a virtual photon, this allows accurate predictions at O(alpha(em)) to be made for leptonic decay rates for pseudoscalar mesons ranging from the pion to the D-s meson. We are able to separate unambiguously and nonpertubatively the pointlike contribution, from the structure-dependent, infrared-safe, terms in the amplitude. The fully nonperturbative O(alpha) improved calculation of the inclusive leptonic decay rates will lead to the determination of the corresponding Cabibbo-Kobayashi-Maskawa matrix elements also at O(alpha(em)). Prospects for a precise evaluation of leptonic decay rates with emission of a hard photon are also very interesting, especially for the decays of heavy D and B mesons for which currently only modeldependent predictions are available to compare with existing experimental data.

Automated summary

The study presents a nonperturbative lattice calculation method for accurately predicting the leptonic decay rates of pseudoscalar mesons, distinguishing contributions from different factors in the amplitude, and also focuses on the evaluation of leptonic decay rates with emission of a hard photon.