1,011 research outputs found
Supersymmetric Extension of the Minimal Dark Matter Model
The minimal dark matter model is given a supersymmetric extension. A super
SU(2)L quintuplet is introduced with its fermionic neutral component still
being the dark matter, the dark matter particle mass is about 19.7 GeV. Mass
splitting among the quintplet due to supersymmetry particles is found to be
negligibly small compared to the electroweak corrections. Other properties of
this supersymmetry model are studied, it has the solutions to the PAMELA and
Fermi-LAT anomaly, the predictions in higher energies need further experimental
data to verify.Comment: 14 pages, 7 figures, accepted for publication in Chinese Physics C,
typos correcte
Decaying Dark Matter can explain the electron/positron excesses
PAMELA and ATIC recently reported excesses in e+ e- cosmic rays. Since the
interpretation in terms of DM annihilations was found to be not easily
compatible with constraints from photon observations, we consider the DM decay
hypothesis and find that it can explain the e+ e- excesses compatibly with all
constraints, and can be tested by dedicated HESS observations of the Galactic
Ridge. ATIC data indicate a DM mass of about 2 TeV: this mass naturally implies
the observed DM abundance relative to ordinary matter if DM is a quasi-stable
composite particle with a baryon-like matter asymmetry. Technicolor naturally
yields these type of candidates.Comment: 20 pages, 7 figure
TeV Scale Singlet Dark Matter
It is well known that stable weak scale particles are viable dark matter
candidates since the annihilation cross section is naturally about the right
magnitude to leave the correct thermal residual abundance. Many dark matter
searches have focused on relatively light dark matter consistent with weak
couplings to the Standard Model. However, in a strongly coupled theory, or even
if the coupling is just a few times bigger than the Standard Model couplings,
dark matter can have TeV-scale mass with the correct thermal relic abundance.
Here we consider neutral TeV-mass scalar dark matter, its necessary
interactions, and potential signals. We consider signals both with and without
higher-dimension operators generated by strong coupling at the TeV scale, as
might happen for example in an RS scenario. We find some potential for
detection in high energy photons that depends on the dark matter distribution.
Detection in positrons at lower energies, such as those PAMELA probes, would be
difficult though a higher energy positron signal could in principle be
detectable over background. However, a light dark matter particle with
higher-dimensional interactions consistent with a TeV cutoff can in principle
match PAMELA data.Comment: 30 pages, 11 figures. Minor changes, references adde
String Necklaces and Primordial Black Holes from Type IIB Strings
We consider a model of static cosmic string loops in type IIB string theory,
where the strings wrap cycles within the internal space. The strings are not
topologically stabilised, however the presence of a lifting potential traps the
windings giving rise to kinky cycloops. We find that PBH formation occurs at
early times in a small window, whilst at late times we observe the formation of
dark matter relics in the scaling regime. This is in stark contrast to previous
predictions based on field theoretic models. We also consider the PBH
contribution to the mass density of the universe, and use the experimental data
to impose bounds on the string theory parameters.Comment: 45 pages, 9 figures, LaTeX; published versio
Non-Abelian Dark Sectors and Their Collider Signatures
Motivated by the recent proliferation of observed astrophysical anomalies,
Arkani-Hamed et al. have proposed a model in which dark matter is charged under
a non-abelian "dark" gauge symmetry that is broken at ~ 1 GeV. In this paper,
we present a survey of concrete models realizing such a scenario, followed by a
largely model-independent study of collider phenomenology relevant to the
Tevatron and the LHC. We address some model building issues that are easily
surmounted to accommodate the astrophysics. While SUSY is not necessary, we
argue that it is theoretically well-motivated because the GeV scale is
automatically generated. Specifically, we propose a novel mechanism by which
mixed D-terms in the dark sector induce either SUSY breaking or a super-Higgs
mechanism precisely at a GeV. Furthermore, we elaborate on the original
proposal of Arkani-Hamed et al. in which the dark matter acts as a messenger of
gauge mediation to the dark sector. In our collider analysis we present
cross-sections for dominant production channels and lifetime estimates for
primary decay modes. We find that dark gauge bosons can be produced at the
Tevatron and the LHC, either through a process analogous to prompt photon
production or through a rare Z decay channel. Dark gauge bosons will decay back
to the SM via "lepton jets" which typically contain >2 and as many as 8
leptons, significantly improving their discovery potential. Since SUSY decays
from the MSSM will eventually cascade down to these lepton jets, the discovery
potential for direct electroweak-ino production may also be improved.
Exploiting the unique kinematics, we find that it is possible to reconstruct
the mass of the MSSM LSP. We also present decay channels with displaced
vertices and multiple leptons with partially correlated impact parameters.Comment: 44 pages, 25 figures, version published in JHE
Dark Matter in split extended supersymmetry
We consider the split extended (N=2) supersymmetry scenario recently proposed
by Antoniadis et al. [hep-ph/0507192] as a realistic low energy framework
arising from intersecting brane models. While all scalar superpartners and
charged gauginos are naturally at a heavy scale, the model low energy spectrum
contains a Higgsino-like chargino and a neutralino sector made out of two
Higgsino and two Bino states. We show that the lightest neutralino is a viable
dark matter candidate, finding regions in the parameter space where its thermal
relic abundance matches the latest determination of the density of matter in
the
Universe by WMAP. We also discuss dark matter detection strategies within
this model: we point out that current data on cosmic-ray antimatter already
place significant constraints on the model, while direct detection is the most
promising technique for the future. Analogies and differences with respect to
the standard split
SUSY scenario based on the MSSM are illustrated.Comment: 14 pages, references added, typos corrected, matches with the
published versio
Gamma-ray and radio tests of the e+e- excess from DM annihilations
PAMELA and ATIC recently reported an excess in e+e- cosmic rays. We show that
if it is due to Dark Matter annihilations, the associated gamma-ray flux and
the synchrotron emission produced by e+e- in the galactic magnetic field
violate HESS and radio observations of the galactic center and HESS
observations of dwarf Spheroidals, unless the DM density profile is
significantly less steep than the benchmark NFW and Einasto profiles.Comment: 16 pages, 4 figures; v2: normalizations fixed in Table 2 and typos
corrected (no changes in the analysis nor the results), some references and
comments added; v3: minor additions, matches published versio
Electroweak baryogenesis, large Yukawas and dark matter
It has recently been shown that the electroweak baryogenesis mechanism is feasible in Standard Model extensions containing extra fermions with large Yukawa couplings. We show here that the lightest of these fermionic fields can naturally be a good candidate for cold dark matter. We find regions in the parameter space where the thermal relic abundance of this particle is compatible with the dark matter density of the Universe as determined by the WMAP experiment. We study direct and indirect dark matter detection for this model and compare with current experimental limits and prospects for upcoming experiments. We find, contrary to the standard lore, that indirect detection searches are more promising than direct ones, and they already exclude part of the parameter space
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