Abstract
The relic density of TeV-scale wino-like neutralino dark matter in the MSSM is subject to potentially large corrections as a result of the Sommerfeld effect. A recently developed framework enables us to calculate the Sommerfeld-enhanced relic density in general MSSM scenarios, properly treating mixed states and multiple co-annihilating channels as well as including off-diagonal contributions. Using this framework, including on-shell one-loop mass splittings and running couplings and taking into account the latest experimental constraints, we perform a thorough study of the regions of parameter space surrounding the well known pure-wino scenario: namely the effect of sfermion masses being non-decoupled and of allowing non-negligible Higgsino or bino components in the lightest neutralino. We further perform an investigation into the effect of thermal corrections and show that these can safely be neglected. The results reveal a number of phenomenologically interesting but so far unexplored regions where the Sommerfeld effect is sizeable. We find, in particular, that the relic density can agree with experiment for dominantly wino neutralino dark matter with masses ranging from 1.7 to beyond 4 TeV. In light of these results the bounds from Indirect Detection on wino-like dark matter should be revisited.
Highlights
The so-called “WIMP miracle” is the observation that a thermally produced, stable, massive particle χ with electroweak interactions (WIMP) naturally accounts for the observed dark matter relic density, if its mass is of order of the electroweak or TeV scale
Away from the pure-wino limit, the lightest neutralino is a mixture of wino, Higgsino and bino eigenstates and interacts which makes the computation of the Sommerfeld effect much more involved. This problem was first approached in refs. [9, 11], a framework that deals systematically with mixed states, multiple co-annihilating states and the corresponding off-diagonal reactions was only developed in refs. [12,13,14], which allowed the computation of the relic density including the Sommerfeld effect with a relative accuracy similar to state-of-the-art computations employing Born cross sections. This was studied in a number of models that interpolate from a pure-wino to a pureHiggsino dark matter (DM) particle [15], but a detailed investigation of the minimal supersymmetric standard model (MSSM) parameter space was left for the future
We have studied the Sommerfeld effect on the relic density of neutralino dark matter beyond the pure-wino limit
Summary
The so-called “WIMP miracle” is the observation that a thermally produced, stable, massive particle χ with electroweak interactions (WIMP) naturally accounts for the observed dark matter relic density, if its mass is of order of the electroweak or TeV scale. Loop effects from electroweak gauge boson exchange are large in non-relativistic scattering before the annihilation of TeV-scale dark matter, and lead to the electroweak Sommerfeld effect [6, 7], which is strong in the wino-like region This has been studied extensively in the purewino limit [6,7,8,9,10], which corresponds to the minimal triplet model. [12,13,14], which allowed the computation of the relic density including the Sommerfeld effect with a relative accuracy similar to state-of-the-art computations employing Born cross sections This was studied in a number of models that interpolate from a pure-wino to a pureHiggsino DM particle [15], but a detailed investigation of the MSSM parameter space was left for the future. We explain why previous work [8, 9] overemphasised the effect
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