Speaker
Description
Radiative leptonic decays of the form P -> l nu gamma, where P
is a charged pseudoscalar meson and l a lepton, are interesting probes of New Physics beyond the SM. When the pseudoscalar P is heavy (e.g. for P=D, Ds, B) and the lepton l is light, the structure-dependent contributions to the decay rate are enhanced w.r.t. the point-like one by a factor (mp/ml)^2, making the corresponding decay rate very sensitive to the internal structure of the decaying meson. As a part of the Soton/RM123 collaboration program to provide an high-precision lattice QCD determination of the
P -> l nu gamma decay amplitude for all heavy mesons, we considered the case P=Ds
and computed the axial (FA) and vector (FV) form factors, which parameterize the
P -> l nu gamma amplitude, over the whole allowed phase space. Our calculation makes use of the gauge-field configurations produced by the ETM collaboration using Nf=2+1+1 flavours of Wilson-clover twisted-mass fermions at maximal twist. Our determination of the Ds=e ne gamma decay rate turns out to be much lower than existing model-dependent calculations, and well within the experimental bound set by the BESIII collaboration.
