Abstract
The Higgs doublet can mediate a long-range interaction between multi-TeV particles coupled to the Weak interactions of the Standard Model, while its emission can lead to very rapid bound-state formation processes and bound-to-bound transitions. Using the rates calculated in a companion paper, here we compute the thermal decoupling of multi-TeV WIMP dark matter coupled to the Higgs, and show that the formation of metastable dark matter bound states via Higgs-doublet emission and their decay decrease the relic density very significantly. This in turn implies that WIMP dark matter may be much heavier than previously anticipated, or conversely that for a given mass, the dark matter couplings to the Higgs may be much lower than previously predicted, thereby altering the dark matter phenomenology. While we focus on a minimal singlet-doublet model in the coannihilation regime, our calculations can be extended to larger multiplets where the effects under consideration are expected to be even more significant.
Highlights
We will focus on a minimal singlet-doublet realisation of this class of scenarios
Using the rates calculated in a companion paper, here we compute the thermal decoupling of multi-TeV WIMP dark matter coupled to the Higgs, and show that the formation of metastable dark matter bound states via Higgs-doublet emission and their decay decrease the relic density very significantly
The exponential increase of σvrel eff due to BSF when the ionisation processes cease, gives rise to a second period of DM destruction that decreases the DM density by two orders of magnitude! In figure 5, we show the timeline of the DM thermal decoupling
Summary
We begin by specifying the model following ref. [35], before summarising the mass eigenstates and interactions in the broken electroweak phase. Since the coupling to Zμ is non-diagonal, with the mass splitting being always much larger than ∼ O(100 keV) for the y values we will consider here (cf section 3), the constraints from direct detection experiments due to this interaction are evaded. [19, 22].) Constraints may arise from electroweak precision observables, and in particular from the contribution to the T parameter While the latter scales as (yL2 − yR2 ) and vanishes in the limit considered here, it may become important for large values of the Yukawa coupling(s) if |yL| |yR| or |yL| |yR|. While a detailed phenomenological analysis is beyond the scope of the present work, our results are important for interpreting the experimental constraints, since they imply a different relation between the DM mass and couplings in order for the observed DM density to be attained via thermal freeze-out
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