  The simplest extension of the standard model consists in adding one singlet
scalar field which mixes with the Higgs boson. O(GeV) masses of the new scalar
carry strong motivation from relaxion, dark matter and inflation models. The
decay of a GeV scalar is, however, notoriously difficult to address since, at
this mass scale, the chiral expansion breaks down and perturbative QCD does not
apply. Existing estimates of the GeV scalar decay rate disagree by several
orders of magnitude. In this work, we perform a new dispersive analysis in
order to strongly reduce these uncertainties and to resolve discrepancies in
earlier results. We will update existing limits on light scalars and future
experimental sensitivities which are in some cases strongly affected by the
new-found decay rates. The meson form factors provided in this work, can be
used to generalize our findings to non-universally coupled light scalars.
