Decay and Detection of a Light Scalar Boson Mixing with the Higgs

TL;DR

This paper performs a dispersive analysis to accurately determine the decay rates of a GeV-scale scalar boson mixing with the Higgs, reducing previous uncertainties and updating experimental limits.

Contribution

It introduces a new dispersive method to precisely calculate the decay rates of light scalar bosons, resolving discrepancies in earlier estimates.

Findings

Reduced uncertainties in GeV scalar decay rates

Updated limits on light scalar particles

Enhanced understanding of scalar-meson interactions

Abstract

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.