On soft contributions to the $B^{-}\to {\gamma }^{\ast }$ form factors

Aoife Bharucha, Danny van Dyk, Eduardo Velásquez

The photoleptonic decay $B^{-}\to \gamma {\ell }^{-}\bar{\nu }$ is the simplest low-energy process that probes the substructure of the $B$ meson, making it an excellent candidate to determine the pa…