A lattice calculation of the branching ratio for $\bar{B}\to K^{\ast }\gamma$

Preliminary results are presented on the calculation of the relevant form factor for the radiative decay $\bar{B}\to K^{\ast }\gamma$ We find that the form factor is weakly dependent on the spectator quark mass. We compare the results obtained for a full chiral extrapolation and where this independence is assumed. Both results are found to be statistically consistent with the experimental data.