Real photon emissions in leptonic decays
Abstract
We present a nonperturbative calculation of the form factors which contribute to the amplitudes for the radiative decays $P\to \ell \bar \nu_\ell \gamma$, where $P$ is a pseudoscalar meson and $\ell$ is a charged lepton. Together with the nonperturbative determination of the virtual photon corrections to the processes $P\to \ell \bar \nu_\ell$, this will allow accurate predictions to be made at $O(\alpha_{em})$ for leptonic decay rates for pseudoscalar mesons ranging from the pion to the $B$ meson. We are able to separate unambiguously the pointlike contribution, the square of which leads to the infrared divergence in the decay rate, from the structure dependent, infraredsafe, terms in the amplitude. The fully nonperturbative, $O(a)$ improved calculation of the inclusive leptonic decay rates will lead to significantly improved precision in the determination of the corresponding CabibboKobayashiMaskawa (CKM) matrix elements. Precise predictions for the 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.
 Publication:

arXiv eprints
 Pub Date:
 August 2019
 arXiv:
 arXiv:1908.10160
 Bibcode:
 2019arXiv190810160D
 Keywords:

 High Energy Physics  Lattice;
 High Energy Physics  Phenomenology