72 research outputs found
Relic density of wino-like dark matter in the MSSM
The relic density of TeV-scale wino-like neutralino dark matter in the MSSM
is subject to potentially large corrections as a result of the Sommerfeld
effect. A recently developed framework enables us to calculate the
Sommerfeld-enhanced relic density in general MSSM scenarios, properly treating
mixed states and multiple co-annihilating channels as well as including
off-diagonal contributions. Using this framework, including on-shell one-loop
mass splittings and running couplings and taking into account the latest
experimental constraints, we perform a thorough study of the regions of
parameter space surrounding the well known pure-wino scenario: namely the
effect of sfermion masses being non-decoupled and of allowing non-negligible
Higgsino or bino components in the lightest neutralino. We further perform an
investigation into the effect of thermal corrections and show that these can
safely be neglected. The results reveal a number of phenomenologically
interesting but so far unexplored regions where the Sommerfeld effect is
sizeable. We find, in particular, that the relic density can agree with
experiment for dominantly wino neutralino dark matter with masses ranging from
1.7 to beyond 4 TeV. In light of these results the bounds from Indirect
Detection on wino-like dark matter should be revisited.Comment: 49 pages, 15 figure
The one-loop and Sommerfeld electroweak corrections to the Wino dark matter annihilation
We compute the present-day Wino dark matter annihilation cross-section
including the one-loop radiative corrections together with the fully treated
electroweak Sommerfeld effect. We discuss what is the consistent way of
incorporating these two corrections simultaneously and why simply using the
running coupling constants values at the Wino mass scale is not correct. The
results show that up to a few TeV scale the full one-loop computation makes the
cross-section smaller up to about 30% with respect to the Sommerfeld enhanced
tree level result and are considerably larger than the tree or one-loop level
without the Sommerfeld effect.Comment: 25 pages, 13 figures; clarifications on the range of validity of the
results, in particular for the annihilation into neutral gauge bosons;
attached tabulated results for the cross-section
Relic densities including Sommerfeld enhancements in the MSSM
We have developed a general formalism to compute Sommerfeld enhancement (SE)
factors for a multi-state system of fermions, in all possible spin
configurations and with generic long-range interactions. We show how to include
such SE effects in an accurate calculation of the thermal relic density for
WIMP dark matter candidates. We apply the method to the MSSM and perform a
numerical study of the relic abundance of neutralinos with arbitrary
composition and including the SE due to the exchange of the W and Z bosons,
photons and Higgses. We find that the relic density can be suppressed by a
factor of a few in a seizable region of the parameter space, mostly for
Wino-like neutralino with mass of a few TeV, and up to an order of magnitude
close to a resonance.Comment: 23 pages, 7 figures; table 1 corrected and rearranged, numerical
results practically unchanged, matches published versio
Background model systematics for the Fermi GeV excess
The possible gamma-ray excess in the inner Galaxy and the Galactic center
(GC) suggested by Fermi-LAT observations has triggered a large number of
studies. It has been interpreted as a variety of different phenomena such as a
signal from WIMP dark matter annihilation, gamma-ray emission from a population
of millisecond pulsars, or emission from cosmic rays injected in a sequence of
burst-like events or continuously at the GC. We present the first comprehensive
study of model systematics coming from the Galactic diffuse emission in the
inner part of our Galaxy and their impact on the inferred properties of the
excess emission at Galactic latitudes and 300 MeV to 500
GeV. We study both theoretical and empirical model systematics, which we deduce
from a large range of Galactic diffuse emission models and a principal
component analysis of residuals in numerous test regions along the Galactic
plane. We show that the hypothesis of an extended spherical excess emission
with a uniform energy spectrum is compatible with the Fermi-LAT data in our
region of interest at CL. Assuming that this excess is the extended
counterpart of the one seen in the inner few degrees of the Galaxy, we derive a
lower limit of ( CL) on its extension away from the GC. We
show that, in light of the large correlated uncertainties that affect the
subtraction of the Galactic diffuse emission in the relevant regions, the
energy spectrum of the excess is equally compatible with both a simple broken
power-law of break energy GeV, and with spectra predicted by the
self-annihilation of dark matter, implying in the case of final
states a dark matter mass of GeV.Comment: 65 pages, 28 figures, 7 table
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