573 research outputs found
Deep XMM Observations of Draco rule out at the 99% Confidence Level a Dark Matter Decay Origin for the 3.5 keV Line
We searched for an X-ray line at energies around 3.5 keV in deep, ~1.6 Msec
XMM-Newton observations of the dwarf spheroidal galaxy Draco. No line was found
in either the MOS or the PN detectors. The data in this energy range are
completely consistent with a single, unfolded power law modeling the particle
background, which dominates at these energies, plus instrumental lines; the
addition of a ~3.5 keV line feature gives no improvement to the fit. The
corresponding upper limit on the line flux rules out a dark matter decay origin
for the 3.5 keV line found in observations of clusters of galaxies and in the
Galactic Center at greater than 99% C.L..Comment: 5 pages, 3 figures, accepted for publication in Monthly Notices of
the Royal Astronomical Society; includes new discussion on Ruchayskiy et al
(2015), arXiv:1512.0721
Synchrotron Emission from Dark Matter Annihilation: Predictions for Constraints from Non-detections of Galaxy Clusters with New Radio Surveys
The annihilation of dark matter particles is expected to yield a broad
radiation spectrum via the production of Standard Model particles in
astrophysical environments. In particular, electrons and positrons from dark
matter annihilation produce synchrotron radiation in the presence of magnetic
fields. Galaxy clusters are the most massive collapsed structures in the
universe, and are known to host G-scale magnetic fields. They are
therefore ideal targets to search for, or to constrain the synchrotron signal
from dark matter annihilation. In this work we use the expected sensitivities
of several planned surveys from the next generation of radio telescopes to
predict the constraints on dark matter annihilation models which will be
achieved in the case of non-detections of diffuse radio emission from galaxy
clusters. Specifically, we consider the Tier 1 survey planned for the Low
Frequency Array (LOFAR) at 120 MHz, the EMU survey planned for the Australian
Square Kilometre Array Pathfinder (ASKAP) at 1.4 GHz, and planned surveys for
APERTIF at 1.4 GHz. We find that, for massive clusters and dark matter masses
GeV, the predicted limits on the annihilation cross section
would rule out vanilla thermal relic models for even the shallow LOFAR Tier 1,
ASKAP, and APERTIF surveys.Comment: accepted to ApJ; removal of LOFAR Tier 2 limits; other minor text
changes; conclusions largely unchange
Lepton Flavor Violation, Neutralino Dark Matter and the Reach of the LHC
We revisit the phenomenology of the Constrained MSSM with right-handed
neutrinos (CMSSMRN). A supersymmetric seesaw mechanism, generating neutrino
masses and sizable lepton flavour violating (LFV) entries is assumed to be
operative. In this scheme, we study the complementarity between the `observable
ranges' of various paths leading to the possible discovery of low energy SUSY:
the reach of the Cern Large Hadron Collider (LHC), the quest for neutralino
dark matter signals and indirect searches through LFV processes. Within the
regions of the CMSSMRN parameter space compatible with all
cosmo-phenomenological requirements, those which are expected to be probed at
the LHC will be typically also accessible to upcoming LFV experiments.
Moreover, parameter space portions featuring a heavy SUSY particle spectrum
could be well beyond LHC reach while leaving LFV searches as the only key to
get a glimpse on SUSY.Comment: 31 pages, 12 figures, LateX; v2: one reference and one comment added;
matches with published versio
Singlet fermion dark matter and electroweak baryogenesis with radiative neutrino mass
The model of radiative neutrino mass with dark matter proposed by one of us
is extended to include a real singlet scalar field. There are then two
important new consequences. One is the realistic possibility of having the
lightest neutral singlet fermion (instead of the lightest neutral component of
the dark scalar doublet) as the dark matter of the Universe. The other is a
modification of the effective Higgs potential of the Standard Model, consistent
with electroweak baryogenesis.Comment: 9 pages, no figure
Supersymmetric Electroweak Baryogenesis Via Resonant Sfermion Sources
We calculate the baryon asymmetry produced at the electroweak phase
transition by quasi-degenerate third generation sfermions in the minimal
supersymmetric extension of the Standard Model. We evaluate constraints from
Higgs searches, from collider searches for supersymmetric particles, and from
null searches for the permanent electric dipole moment (EDM) of the electron,
of the neutron and of atoms. We find that resonant sfermion sources can in
principle provide a large enough baryon asymmetry in various corners of the
sfermion parameter space, and we focus, in particular, on the case of large
, where third-generation down-type (s)fermions become relevant. We
show that in the case of stop and sbottom sources, the viable parameter space
is ruled out by constraints from the non-observation of the Mercury EDM. We
introduce a new class of CP violating sources, quasi-degenerate staus, that
escapes current EDM constraints while providing large enough net chiral
currents to achieve successful "slepton-mediated" electroweak baryogenesis.Comment: 35 pages, 9 figures; v2: several revisions, but conclusions
unchanged. Matches version published in PR
A Statistical Analysis of Supersymmetric Dark Matter in the MSSM after WMAP
We study supersymmetric dark matter in the general flavor diagonal MSSM by
means of an extensive random scan of its parameter space. We find that, in
contrast with the standard mSUGRA lore, the large majority of viable models
features either a higgsino or a wino-like lightest neutralino, and yields a
relic abundance well below the WMAP bound. Among the models with neutralino
relic density within the WMAP range, higgsino-like neutralinos are still
dominant, though a sizeable fraction of binos is also present. In this latter
case, relic density suppression mechanisms are shown to be essential in order
to obtain the correct neutralino abundance. We then carry out a statistical
analysis and a general discussion of neutralino dark matter direct detection
and of indirect neutralino detection at neutrino telescopes and at antimatter
search experiments. We point out that current data exclude only a marginal
portion of the viable parameter space, and that models whose thermal relic
abundance lies in the WMAP range will be significantly probed only at future
direct detection experiments. Finally, we emphasize the importance of relic
density enhancement mechanisms for indirect detection perspectives, in
particular at future antimatter search experiments.Comment: 39 pages, 25 figure
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