$B_sto D_s^{(*)}l u$ Form Factors with Heavy HISQ Quarks

We present progress on an ongoing calculation of the $B_sto D_s^{(*)} l u$ form factors calculated on the $n_f=2+1+1$ MILC ensembles and using the Highly Improved Staggered Quark action for all valence quarks. We perform the calculation at a range of $b$ quark masses (and lattice spacings) so that we can extrapolate to the physical $b$-quark mass.