Calculation of $B^0 \to K^{*0} \mu^+ \mu^-$ and $B_s^0 \to \phi \mu^+ \mu^-$ observables using form factors from lattice QCD

Understand

We calculate the differential branching fractions and angular distributions of the rare decays $B^0 \to K^{*0} \mu^+ \mu^-$ and $B_s^0 \to \phi \mu^+ \mu^-$, using for the first time form factors from unquenched lattice QCD.

• We focus on the kinematic region where the $K^*$ or $\phi$ recoils softly; there the newly available form factors are most precise and the nonlocal matrix elements can be included via an operator product expansion.
• Our results for the differential branching fractions calculated in the Standard Model are higher than the experimental data.
• We consider the possibility that the deviations are caused by new physics, and perform a fit of the Wilson coefficients $C_9$ and $C_9^\prime$ to the experimental data for multiple $B^0 \to K^{*0} \mu^+ \mu^-$ and $B_s^0 \to \phi \mu^+ \mu^-$ observables.