8,652 research outputs found
Supersymmetric Higgs-portal and X-ray lines
We consider a Dirac singlet fermion as thermal dark matter for explaining the
X-ray line in the context of a supersymmetric Higgs-portal model or a
generalized Dirac NMSSM. The Dirac singlet fermion gets a mass splitting due to
their Yukawa couplings to two Higgs doublets and their superpartners,
Higgsinos, after electroweak symmetry breaking. We show that a correct relic
density can be obtained from thermal freeze-out, due to the co-annihilation
with Higgsinos for the same Yukawa couplings. We discuss the phenomenology of
the Higgsinos in this model such as displaced vertices at the LHC.Comment: 15 pages, 4 figures, references adde
Cluster X-ray line at from axion-like dark matter
The recently reported X-ray line signal at
from a stacked spectrum of various galaxy clusters and the Andromeda galaxy may
be originating from a decaying dark matter particle of the mass . A
light axion-like scalar is suggested as a natural candidate for dark matter and
its production mechanisms are closely examined. We show that the right amount
of axion relic density with the preferred parameters, and , can be naturally obtainable
from the decay of inflaton. If the axions were produced from the saxion decay,
it could not have constituted the total relic density due to the bound from
structure formation. Nonetheless, the saxion decay is an interesting
possibility, because the line and dark radiation can be
addressed simultaneously, being consistent with the Planck data. Small
misalignment angles of the axion, ranging between depending on the reheating temperature, can also be the source of
axion production. The model with axion misalignment can satisfy the constraints
for structure formation and iso-curvature perturbation.Comment: 14 pages, significant changes in the form, matched to the journal
versio
Gravity-mediated (or composite) dark matter
Dark matter could have an electroweak origin, yet it could communicate with the visible sector exclusively through gravitational interactions. In a setup addressing the hierarchy problem, we propose a new dark-matter scenario where gravitational mediators, arising from the compactification of extra dimensions, are responsible for dark-matter interactions and its relic abundance in the Universe. We write an explicit example of this mechanism in warped extra dimensions and work out its constraints. We also develop a dual picture of the model, based on a four-dimensional scenario with partial compositeness. We show that gravity-mediated dark matter is equivalent to a mechanism of generating viable dark matter scenarios in a strongly coupled, near-conformal theory, such as in composite Higgs models
-meson anomalies and Higgs physics in flavored model
We consider a simple extension of the Standard Model with flavor-dependent
, that has been proposed to explain some of -meson anomalies recently
reported at LHCb. The charge is chosen as a linear combination of
anomaly-free and . In this model, the flavor structure
in the SM is restricted due to flavor-dependent charges, in particular,
quark mixings are induced by a small vacuum expectation value of the extra
Higgs doublet. As a result, it is natural to get sizable flavor-violating
Yukawa couplings of heavy Higgs bosons involving the bottom quark. In this
article, we focus on the phenomenology of the Higgs sector of the model
including extra Higgs doublet and singlet scalars. We impose various bounds on
the extended Higgs sector from Higgs and electroweak precision data, -meson
mixings and decays as well as unitarity and stability bounds, then discuss the
productions and decays of heavy Higgs bosons at the LHC.Comment: 40 pages, 11 figures, 1 table; v2: references added; v3: accepted
version for publication in EPJ
Diboson Excesses Demystified in Effective Field Theory Approach
We study the collider implication of a neutral resonance which decays to
several diboson final states such as , , and via a
minimal set of effective operators. We consider both CP-even and CP-odd bosonic
states with spin 0, 1, or 2. The production cross sections for the bosonic
resonance states are obtained with the effective operators involving gluons
(and quarks), and the branching fractions are obtained with the operators
responsible for the interactions with electroweak gauge bosons. We demonstrate
that each scenario allows for a broad parameter space which could accommodate
the recently-reported intriguing excesses in the ATLAS diboson final states,
and discuss how the CP states and spin information of the resonance can be
extracted at the LHC run II.Comment: 22 pages, 6 figures, main text slightly modified with results
unchange
Fermi Gamma Ray Line at 130 GeV from Axion-Mediated Dark Matter
We consider a singlet Dirac fermion with Peccei-Quinn(PQ) symmetry as dark
matter. A singlet complex scalar is introduced to mediate between dark matter
and the SM through Higgs portal interaction and electroweak PQ anomalies. We
show that a resonant annihilation of dark matter with axion mediation can
explain the monochromatic photon line of the Fermi LAT data at 130 GeV by
anomaly interactions while the annihilation cross section with Higgs portal
interaction is p-wave suppressed. We discuss the interplay between the direct
detection of the fermion dark matter and the collider search of Higgs-like
scalars. We also present a ultra-violet completion of the dark matter model
into the NMSSM with PQ symmetry.Comment: 22 pages, 9 figures, To be published in Phys. Rev.
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