61 research outputs found
Dark matter within the minimal flavour violation ansatz
Minimal Flavour Violation hypothesis can provide an attractive framework for
Dark Matter (DM). We consider scalar DM candidates carrying flavour quantum
numbers and whose representation under the flavour group guarantees DM
stability. They interact with the Standard Model fields through Higgs portal at
renormalisable level and also to quarks through dimension-6 operators. We
provide a systematic analysis of the viable parameter space for the DM fields,
which are triplet of the flavour group, considering several DM-quark
interactions. In this framework, we analyse in which cases the viable parameter
space differs from Higgs portal models thanks to the underlying flavour
structure. In contrast to minimal Higgs portal scenarios, we find that light DM
in the GeV mass range as well as heavier candidates above Higgs resonance could
be allowed by colliders, direct and indirect DM detection searches as well as
flavour constraints. The large mass regime above the top mass could even be
beyond the reach of future experiments such as Xenon 1T.Comment: 11 pages, 2 figures; v2: references added, version published on
Phys.Lett.
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
A feeble window on leptophilic dark matter
In this paper we study a leptophilic dark matter scenario involving feeble
dark matter coupling to the Standard Model (SM) and compressed dark
matter-mediator mass spectrum. We consider a simplified model where the SM is
extended with one Majorana fermion, the dark matter, and one charged scalar,
the mediator, coupling to the SM leptons through a Yukawa interaction. We first
discuss the dependence of the dark matter relic abundance on the Yukawa
coupling going continuously from freeze-in to freeze-out with an intermediate
stage of conversion driven freeze-out. Focusing on the latter, we then exploit
the macroscopic decay length of the charged scalar to study the resulting
long-lived-particle signatures at collider and to explore the experimental
reach on the viable portion of the parameter space.Comment: 32 pages, 10 figure
Scalar Dark Matter Models with Significant Internal Bremsstrahlung
There has been interest recently on particle physics models that may give
rise to sharp gamma ray spectral features from dark matter annihilation.
Because dark matter is supposed to be electrically neutral, it is challenging
to build weakly interacting massive particle models that may accommodate both a
large cross section into gamma rays at, say, the Galactic center, and the right
dark matter abundance. In this work, we consider the gamma ray signatures of a
class of scalar dark matter models that interact with Standard Model dominantly
through heavy vector-like fermions (the vector-like portal). We focus on a real
scalar singlet S annihilating into lepton-antilepton pairs. Because this
two-body final-state annihilation channel is d-wave suppressed in the chiral
limit, we show that virtual internal bremsstrahlung emission of a gamma ray
gives a large correction, both today and at the time of freeze-out. For the
sake of comparison, we confront this scenario to the familiar case of a
Majorana singlet annihilating into light lepton-antilepton pairs, and show that
the virtual internal bremsstrahlung signal may be enhanced by a factor of (up
to) two orders of magnitude. We discuss the scope and possible generalizations
of the model.Comment: 25 pages, 10 figures, typos corrected, added references, matching
version accepted by JCA
Non-Cold Dark Matter from Primordial Black Hole Evaporation
Dark matter coupled solely gravitationally can be produced through the decay
of primordial black holes in the early universe. If the dark matter is lighter
than the initial black hole temperature, it could be warm enough to be subject
to structure formation constraints. In this paper we perform a more precise
determination of these constraints. We first evaluate the dark matter
phase-space distribution, without relying on the instantaneous decay
approximation. We then interface this phase-space distribution with the
Boltzmann code CLASS to extract the corresponding matter power spectrum, which
we find to match closely those of warm dark matter models, albeit with a
different dark matter mass. This mapping allows us to extract constraints from
Lyman- data without the need to perform hydrodynamical simulations. We
robustly rule out the possibility, consistent with previous analytic estimates,
of primordial black holes having come to dominate the energy density of the
universe and simultaneously given rise to all the DM through their decay.
Consequences and implications for dark radiation and leptogenesis are also
briefly discussed.Comment: 33 pages, 4 figure
Dark Matter Constraints on Composite Higgs Models
In composite Higgs models the pseudo-Nambu-Goldstone Boson (pNGB) nature of
the Higgs field is an interesting alternative for explaning the smallness of
the electroweak scale with respect to the beyond the Standard Model scale. In
non-minimal models additional pNGB states are present and can be a Dark Matter
(DM) candidate, if there is an approximate symmetry suppressing their decay.
Here we assume that the low energy effective theory (for scales much below the
compositeness scale) corresponds to the Standard Model with a pNGB Higgs
doublet and a pNGB DM multiplet. We derive general effective DM Lagrangians for
several possible DM representations (under the SM gauge group), including the
singlet, doublet and triplet cases. Within this framework we discuss how the DM
observables (relic abundance, direct and indirect detection) constrain the
dimension-6 operators induced by the strong sector assuming that DM behaves as
a Weakly Interacting Particle (WIMP) and that the relic abundance is settled
through the freeze-out mechanism. We also apply our general results to two
specific cosets: and , which contain a
singlet and doublet DM candidate, respectively. In particular we show that if
compositeness is a solution to the little hierarchy problem, representations
larger than the triplet are strongly disfavored. Furthermore, we find that
composite models can have viable DM candidates with much smaller direct
detection cross-sections than their non-composite counterparts, making DM
detection much more challenging.Comment: version accepted by JHE
Warm dark matter and the ionization history of the Universe
In warm dark matter scenarios structure formation is suppressed on small
scales with respect to the cold dark matter case, reducing the number of
low-mass halos and the fraction of ionized gas at high redshifts and thus,
delaying reionization. This has an impact on the ionization history of the
Universe and measurements of the optical depth to reionization, of the
evolution of the global fraction of ionized gas and of the thermal history of
the intergalactic medium, can be used to set constraints on the mass of the
dark matter particle. However, the suppression of the fraction of ionized
medium in these scenarios can be partly compensated by varying other
parameters, as the ionization efficiency or the minimum mass for which halos
can host star-forming galaxies. Here we use different data sets regarding the
ionization and thermal histories of the Universe and, taking into account the
degeneracies from several astrophysical parameters, we obtain a lower bound on
the mass of thermal warm dark matter candidates of keV, or keV for the case of sterile neutrinos non-resonantly produced in the early
Universe, both at 90\% confidence level.Comment: 15 pages, 5 figure
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