$h→\mathrm{ϒ}γ$ decay: Smoking gun signature of a wrong-sign $hb\overline{b}$ coupling

We perform a model-independent study of new physics effects in the Higgs decay $h\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}\ensuremath{\gamma}$, focusing on scenarios that spoil the accidental cancellation between the direct and indirect amplitudes. After imposing all existing constraints from Higgs production and decay measurements, we find that a wrong-sign $hb\overline{b}$ coupling is the only viable scenario capable of enhancing the $h\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}\ensuremath{\gamma}$ decay width by nearly 2 orders of magnitude. Therefore, an observation of a significantly enhanced $h\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}\ensuremath{\gamma}$ rate at the LHC or future colliders would provide unambiguous evidence for a wrong-sign $hb\overline{b}$ coupling, directly pointing to the presence of an extended Higgs sector.