$D_s$ to $\phi$ and other transitions from lattice QCD

We have studied transitions between vector and pseudoscalar mesons using the HISQ action for the valence quarks. We have calculated all of the axial and vector form factors that appear in the decay rate for $D_s \to \phi \ell \nu$ over the full $q^2$ range and compared them to the shape of the experimental decay distributions. We use nonperturbatively normalised currents for the vector and axial vector currents. The same set up for the three point correlations functions also allow us to study radiative decays and we have calculated the decay rate for $J/\psi \to \eta_c \gamma$.