Prospects for disentangling long- and short-distance effects in the decays $B\to K^* \mu^+\mu^-$

Theory uncertainties on non-local hadronic effects limit the New Physics discovery potential of the rare decays B → K$^{∗}$μ$^{+}$μ$^{−}$. We investigate prospects to disentangle New Physics effects in the short-distance coefficients from these effects. Our approach makes use of an event-by-event amplitude analysis, and relies on a particular parametrisation of the non-local contributions. We find that non-standard effects in the short-distance coefficients can be successfully disentangled from non-local hadronic effects. The impact of the truncation on the parametrisation of non-local contributions to the Wilson coefficients are for the first time systematically examined and prospects for their precise determination are discussed. Theoretical inputs on the non-local matrix elements beyond the physically- accessible phase space are crucial to stabilise the determination of Wilson coefficients, while we find that physical observables are unaffected by these uncertainties. Compared to other methods, our approach provides for a more precise extraction of the angular observables from data.