Abstract
We describe the automation of the calculation of perturbative unitarity constraints including scalars that have colour charges, and its release in SARAH4.14.4. We apply this, along with vacuum stability constraints, to a simple dark matter model with colourful mediators and interesting decays, and show how it leads to a bound on a thermal relic dark matter mass well below the classic Griest-Kamionkowski limit.
Highlights
Unitarity of scattering amplitudes has long been used to constrain the masses and couplings of thermal relic dark matter (DM) particles [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
The typical approach to constraining a new model with such scalars, would be to use vacuum stability to constrain the size of cubic couplings, which in turn push the theory to large quartic couplings; large scattering-momentum unitarity to give an upper bound on the quartic couplings; and the dark matter annihilation cross-section is limited by the values of both
To illustrate the new capabilities in SARAH and test the idea of a maximum dark matter mass, we shall take a model with colourful scalar mediators, but where the dark matter candidate is the usual scalar singlet S with a Z2 symmetry
Summary
Unitarity of scattering amplitudes has long been used to constrain the masses and couplings of thermal relic dark matter (DM) particles [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. The typical approach to constraining a new model with such scalars, would be to use vacuum stability to constrain the size of cubic couplings, which in turn push the theory to large quartic couplings; large scattering-momentum unitarity to give an upper bound on the quartic couplings; and the dark matter annihilation cross-section is limited by the values of both (since it can proceed via both quartic and s/t/u-channel interactions). This reasoning is reinforced, as discussed for example in Ref.
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