76 research outputs found
Large contributions to dark matter annihilation from three-body final states
The annihilation rate of dark matter particles plays a crucial role in dark
matter studies, for it determines their relic density and their indirect
detection signal. In this paper, we show that this annihilation rate can
receive large additional contributions from three-body final states consisting
of a real and a virtual massive particle, such as WW* (Wf \bar f') and t \bar
t* (tW\bar b). We consider two specific examples, from the singlet model and
the MSSM, and find that, due to the new three-body final state contributions,
the prediction for the relic density may decrease by more than a factor two,
whereas the present dark matter annihilation rate gets enhanced by up to two
orders of magnitude. Some of the implications of these results are briefly
discussed.Comment: 6 page
Inverse decays and the relic density of the sterile sneutrino
We consider a weak scale supersymmetric seesaw model where the Higgsino is
the next-to-lightest supersymmetric particle and the right-handed sneutrino is
the dark matter candidate. It is shown that, in this model, inverse decays,
which had been previously neglected, may suppress the sneutrino relic density
by several orders of magnitude. After including such processes and numerically
solving the appropriate Boltzmann equation, we study the dependence of the
relic density on the mu parameter, the sneutrino mass, and the neutrino Yukawa
coupling. We find that, even though much smaller than in earlier calculations,
the sneutrino relic density is still larger than the observed dark matter
density.Comment: 15 pages, 4 figure
Singlet-Doublet Dirac Dark Matter
We analyze a simple extension of the Standard Model where the dark matter
particle is a Dirac fermion that is mixture of a singlet and an SU(2) doublet.
The model contains only four free parameters: the singlet and the doublet
masses and two new Yukawa couplings. Direct detection bounds in this model are
very strong and require the dark matter particle to be singlet-like. As a
result, its relic density has to be obtained via coannihilations with the
doublet. We find that the dark matter mass should be below 750 GeV, that the
singlet-doublet mass difference cannot exceed 9%, and that direct detection
experiments offer the best chance to probe this scenario. Finally, we also show
that this model can effectively arise in well-motivated extensions of the
Standard Model.Comment: 14 page
Scalar dark matter in the B-L model
The B-L extension of the Standard Model requires the existence of
right-handed neutrinos and naturally realizes the seesaw mechanism of neutrino
mass generation. We study the possibility of explaining the dark matter in this
model with an additional scalar field that is a singlet of the Standard Model
but charged under . An advantage of this scenario is that the
stability of the dark matter can be guaranteed by appropriately choosing its
B-L charge, without the need of an extra ad hoc discrete symmetry. We
investigate in detail the dark matter phenomenology of this model. We show that
the observed dark matter density can be obtained via gauge or scalar
interactions, and that semi-annihilations could play an important role in the
latter case. The regions consistent with the dark matter density are determined
in each instance and the prospects for detection in future experiments are
analyzed. If dark matter annihilations are controlled by the B-L gauge
interaction, the mass of the dark matter particle should lie below 5 TeV and
its direct detection cross section can be easily probed by XENON1T; if instead
they are controlled by scalar interactions, the dark matter mass can be much
larger and the detection prospects are less certain. Finally, we show that this
scenario can be readily extended to accommodate multiple dark matter particles.Comment: 24 page
The inert doublet model of dark matter revisited
The inert doublet model, a minimal extension of the Standard Model by a
second higgs doublet with no direct couplings to quarks or leptons, is one of
the simplest scenarios that can explain the dark matter. In this paper, we
study in detail the impact of dark matter annihilation into three-body final
state on the phenomenology of the inert doublet model. We find that this new
annihilation mode dominates, in a relevant portion of the parameter space, over
those into two-body final states considered in previous analysis. As a result,
the computation of the relic density is modified and the viable regions of the
model are displaced. After obtaining the genuine viable regions for different
sets of parameters, we compute the direct detection cross section of inert
higgs dark matter and find it to be up to two orders of magnitude smaller than
what is obtained for two-body final states only. Other implications of these
results, including the modification to the decay width of the higgs and to the
indirect detection signatures of inert higgs dark matter, are also briefly
considered. We demonstrate, therefore, that the annihilation into three-body
final state can not be neglected, as it has a important impact on the entire
phenomenology of the inert doublet model.Comment: 22 pages, format changed, more detailed discussion in general,
figures and references adde
Gamma ray lines: what will they tell us about SUSY?
Neutralino dark matter can be indirectly detected by observing the gamma ray
lines from the annihilation processes XX-->gg and XX-->gZ. In this paper we
study the implications that the observation of these two lines could have for
the determination of the supersymmetric parameter space. Within the minimal
supergravity framework, we find that, independently of the dark matter
distribution in the Galaxy, such observations by themselves would allow to
differentiate between the coannihilation region, the funnel region, and the
focus point region. As a result, several restrictions on the msugra parameters
can be derived. Within a more general MSSM scenario, we show that the
observation of gamma-ray lines might be used to discriminate between a bino-, a
wino-, and a higgsino-like neutralino, with important consequences for
cosmology and for models of supersymmetry breaking. The detection of the gamma
ray lines, therefore, will not only provide an unmistakable signature of dark
matter, it will also open a new road toward the determination of supersymmetric
parameters.Comment: 19 pages, 10 figure
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