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The leading-order electromagnetic and strong isospin-breaking corrections to the ratio of $K_{mu 2}$ and $pi_{mu 2}$ decay rates are evaluated for the first time on the lattice, following a method recently proposed. The lattice results are obtained using the gauge ensembles produced by the European Twisted Mass Collaboration with $N_f = 2 + 1 + 1$ dynamical quarks. Systematics effects are evaluated and the impact of the quenched QED approximation is estimated. Our result for the correction to the tree-level $K_{mu 2} / pi_{mu 2}$ decay ratio is $-1.22,(16) %$ to be compared to the estimate $-1.12,(21) %$ based on Chiral Perturbation Theory and adopted by the Particle Data Group.
RBC/UKQCD is preparing a calculation of leptonic decay rates including isospin breaking corrections using a perturbative approach to include NLO contributions from QED effects. We present preliminary numerical results for a contribution to the lepton
The leading electromagnetic (e.m.) and strong isospin-breaking corrections to the $pi^+ to mu^+ u[gamma]$ and $K^+ to mu^+ u[gamma]$ leptonic decay rates are evaluated for the first time on the lattice. The results are obtained using gauge ensemble
We present a non-perturbative lattice calculation of the form factors which contribute to the amplitudes for the radiative decays $Pto ell bar u_ell gamma$, where $P$ is a pseudoscalar meson and $ell$ is a charged lepton. Together with the non-pertu
We report lattice results of $D_s$ meson semi-leptonic decay form factors to $eta$ and $eta$ mesons. This decay process contains disconnected fermion loops, which are challenging in lattice calculations. Our result shows that the disconnected loops give significant contributions to the form factors.
In Carrasco et al. we have recently proposed a method to calculate $O(e^2)$ electromagnetic corrections to leptonic decay widths of pseudoscalar mesons. The method is based on the observation that the infrared divergent contributions (that appear at