74 research outputs found
Pionic Dark Matter
We study a phenomenological model where the lightest dark matter (DM)
particles are the pseudo-Goldstone excitations associated with a spontaneously
broken symmetry, and transforming linearly with respect to an unbroken group H.
For definiteness we take H = SU(N) and assume the Goldstone particles are
bosons; in parallel with QCD, we refer to these particles as dark-matter pions.
This scenario is in contrast to the common assumption that DM fields transform
linearly under the full symmetry of the model. We illustrate the formalism by
treating in detail the case of H = SU(2), in particular we calculate all the
interactions relevant for the Boltzmann equations, which we solve numerically;
we also derive approximate analytic solutions and show their consistency with
the numerical results. We then compare the results with the constraints derived
from the cold DM and direct detection experiments and derive the corresponding
restrictions on the model parameters.Comment: 35 pages, 15 figure
Multipartite Dark Matter with Scalars, Fermions and signatures at LHC
Basic idea of this analysis is to achieve a two-component dark matter (DM)
framework composed of a scalar and a fermion, with non-negligible DM-DM
interaction contributing to thermal freeze out (hence relic density), but
hiding them from direct detection bounds. We therefore augment the Standard
Model (SM) with a scalar singlet () and three vectorlike fermions: two
singlets () and a doublet (). Stability of the two DM
components is achieved by a discrete symmetry, under which the additional fields transform
suitably. Fermion fields having same charge ( in the model) mix after electroweak
symmetry breaking (EWSB) and the lightest component becomes one of the DM
candidates, while scalar singlet is the other DM component connected to
visible sector by Higgs portal coupling. The heavy fermion () plays the
role of mediator to connect the two DM candidates through Yukawa interaction.
This opens up a large parameter space for the heavier DM component through
DM-DM conversion. Hadronically quiet dilepton signature, arising from the
fermion dark sector, can be observed at Large Hadron Collider (LHC) aided by
the presence of a lighter scalar DM component, satisfying relic density and
direct search bounds through DM-DM conversion.Comment: A section discussing the possible connection to inflation is added.
The version is published in JHE
Two-Component Dark Matter
We study an extension of the Standard Model (SM) with two interacting cold
Dark Matter (DM) candidates: a neutral Majorana fermion () and a neutral
scalar singlet (). The scalar interacts with the SM through
the "Higgs portal" coupling while at the tree level interacts only with
through Yukawa interactions. The relic abundance of and
is found by solving the Boltzmann equations numerically; for the case
we also derive a reliable approximate analytical solution.
Effects of the interaction between the two DM components are discussed. A scan
over the parameter space is performed to determine the regions consistent with
the WMAP data for DM relic abundance, and with the XENON100 direct detection
limits for the DM-nucleus cross section. We find that although a large region
of the parameter space is allowed by the WMAP constraints, the XENON100 data
severely restricts the parameter space. Taking into account only amplitudes
generated at the tree level one finds three allowed regions for the scalar
mass: GeV (corresponding to the vicinity of the Higgs
boson resonance responsible for annihilation into SM
particles), GeV and m_\varphi \gesim 3 TeV. 1-loop
induced -nucleon scattering has been also calculated and discussed. A
possibility of DM direct detection by the CREST-II experiment was considered.Comment: 22 pages, 17 figures; v2: references added, published in JHEP, v3:
misspelled authors name correcte
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