Hunting for [Formula: see text] imprints on the [Formula: see text] dimuon spectrum

We investigate the possibility of indirectly constraining the [Formula: see text] decay rate using precise data on the [Formula: see text] dimuon spectrum. To this end, we estimate the distortion of the spectrum induced by the [Formula: see text] re-scattering process, and propose a method to simultaneously constrain this (non-standard) contribution and the long-distance effects associated to hadronic intermediate states. The latter are constrained using the analytic properties of the amplitude combined with data and perturbative calculations. Finally, we estimate the sensitivity expected at the LHCb experiment with present and future datasets. We find that constraints on the branching fraction of [Formula: see text] , competitive with current direct bounds, can be achieved with the current dataset, while bounds of [Formula: see text] could be obtained with the LHCb upgrade-II luminosity.