9 research outputs found
A gobal fit to the anomalous magnetic moment, Higgs limit and b->s gamma in the constrained MSSM
New data on the anomalous magnetic moment of the muon together with the b->s
gamma decay rate and Higgs limits are considered within the supergravity
inspired constrained minimal supersymmetric model. We perform a global
statistical chi2 analysis of these data and show that the allowed region of
parameter space is bounded from below by the Higgs limit, which depends on the
trilinear coupling and from above by the anomalous magnetic moment.Comment: 3 pages, To appear in Proc. of SUSY01, Dubna (Russia
Long-lived Charginos in the Focus-point Region of the MSSM Parameter Space
We analyse the possibility to get light long-lived charginos within the
framework of the MSSM with gravity mediated SUSY breaking. We find out that
this possibility can be realized in the so-called focus-point region of
parameter space. The mass degeneracy of higgsino-like chargino and two
higgsino-like neutralinos is the necessary condition for a long lifetime. It
requires the fine-tuning of parameters, but being a single additional
constraint in the whole parameter space it can be fulfilled in the Constrained
MSSM along the border line where radiative electroweak symmetry breaking fails.
In a narrow band close to the border line the charginos are long-lived
particles. The cross-sections of their production and co-production at the LHC
via electroweak interaction reach a few tenth of pb.Comment: LaTeX, 11 pages, 11 eps figure
Two photon annihilation of Kaluza-Klein dark matter
We investigate the fermionic one-loop cross section for the two photon
annihilation of Kaluza-Klein (KK) dark matter particles in a model of universal
extra dimensions (UED). This process gives a nearly mono-energetic gamma-ray
line with energy equal to the KK dark matter particle mass. We find that the
cross section is large enough that if a continuum signature is detected, the
energy distribution of gamma-rays should end at the particle mass with a peak
that is visible for an energy resolution of the detector at the percent level.
This would give an unmistakable signature of a dark matter origin of the
gamma-rays, and a unique determination of the dark matter particle mass, which
in the case studied should be around 800 GeV. Unlike the situation for
supersymmetric models where the two-gamma peak may or may not be visible
depending on parameters, this feature seems to be quite robust in UED models,
and should be similar in other models where annihilation into fermions is not
helicity suppressed. The observability of the signal still depends on largely
unknown astrophysical parameters related to the structure of the dark matter
halo. If the dark matter near the galactic center is adiabatically contracted
by the central star cluster, or if the dark matter halo has substructure
surviving tidal effects, prospects for detection look promising.Comment: 17 pages, 3 figures; slightly revised versio
Adiabatic compression and indirect detection of supersymmetric dark matter
Recent developments in the modelling of the dark matter distribution in our
Galaxy point out the necessity to consider some physical processes to satisfy
observational data. In particular, models with adiabatic compression, which
include the effect of the baryonic gas in the halo, increase significantly the
dark matter density in the central region of the Milky Way. On the other hand,
the non-universality in scalar and gaugino sectors of supergravity models can
also increase significantly the neutralino annihilation cross section. We show
that the combination of both effects gives rise to a gamma-ray flux arising
from the Galactic Center largely reachable by future experiments like GLAST. We
also analyse in this framework the EGRET excess data above 1 GeV, as well as
the recent data from CANGAROO and HESS. The analysis has been carried out
imposing the most recent experimental constraints, such as the lower bound on
the Higgs mass, the \bsg branching ratio, and the muon . In addition, the
recently improved upper bound on has also been taken
into account. The astrophysical (WMAP) bounds on the dark matter density have
also been imposed on the theoretical computation of the relic neutralino
density through thermal production.Comment: 32 pages, 11 figures, final version to appear in JCA
Dark Matter and the CACTUS Gamma-Ray Excess from Draco
The CACTUS atmospheric Cherenkov telescope collaboration recently reported a
gamma-ray excess from the Draco dwarf spheroidal galaxy. Draco features a very
low gas content and a large mass-to-light ratio, suggesting as a possible
explanation annihilation of weakly interacting massive particles (WIMPs) in the
Draco dark-matter halo. We show that with improved angular resolution, future
measurements can determine whether the halo is cored or cuspy, as well as its
scale radius. We find the relevant WIMP masses and annihilation cross sections
and show that supersymmetric models can account for the required gamma-ray
flux. The annihilation cross section range is found to be not compatible with a
standard thermal relic dark-matter production. We compute for these
supersymmetric models the resulting Draco gamma-ray flux in the GLAST energy
range and the rates for direct neutralino detection and for the flux of
neutrinos from neutralino annihilation in the Sun. We also discuss the
possibility that the bulk of the signal detected by CACTUS comes from direct
WIMP annihilation to two photons and point out that a decaying-dark-matter
scenario for Draco is not compatible with the gamma-ray flux from the Galactic
center and in the diffuse gamma-ray background.Comment: 24 pages, 10 figures; version accepted for publication in JCA
Collider, direct and indirect detection of supersymmetric dark matter
We present an overview of supersymmetry searches, both at collider
experiments and via searches for dark matter (DM). We focus on three DM
possibilities in the SUSY context: the thermally produced neutralino, a mixture
of axion and axino, and the gravitino, and compare and contrast signals that
may be expected at colliders, in direct detection (DD) experiments searching of
DM relics left over from the Big Bang, and indirect detection (ID) experiments
designed to detect the products of DM annihilations within the solar interior
or galactic halo. Detection of DM particles using multiple strategies provides
complementary information that may shed light on the new physics associated
with the dark matter sector. In contrast to the mSUGRA model where the measured
cold DM relic density restricts us to special regions mostly on the edge of the
m_0-m_{1/2} plane, the entire parameter plane becomes allowed if the
universality assumption is relaxed in models with just one additional
parameter. Then, thermally produced neutralinos with a well-tempered mix of
wino, bino and higgsino components, or with a mass adjusted so that their
annihilation in the early universe is Higgs-resonance-enhanced, can be the DM.
Well-tempered neutralinos typically yield heightened rates for DD and ID
experiments compared to generic predictions from minimal supergravity. If
instead DM consists of axinos (possibly together with axions) or gravitinos,
then there exists the possibility of detection of quasi-stable next-to-lightest
SUSY particles at colliding beam experiments, with especially striking
consequences if the NLSP is charged, but no DD or ID detection. The exception
for mixed axion/axino DM is that DD of axions may be possible.Comment: 28 pages, 11 eps figures; invited contribution to NJP Focus Issue on
"Dark Matter and Particle Physics
EGRET Excess of Diffuse Galactic Gamma Rays as Tracer of Dark Matter
The public data from the EGRET space telescope on diffuse Galactic gamma rays in the energy range from 0.1 to 10 GeV are reanalyzed with the purpose of searching for signals of Dark Matter annihilation (DMA). The analysis confirms the previously observed excess for energies above 1 GeV in comparison with the expectations from conventional Galactic models. In addition, the excess was found to show all the key features of a signal from Dark Matter Annihilation (DMA): a) the excess is observable in all sky directions and has the same shape everywhere, thus pointing to a common source; b) the shape corresponds to the expected spectrum of the annihilation of non-relativistic massive particles into - among others - neutral mesons, which decay into photons. From the energy spectrum of the excess we deduce a WIMP mass between 50 and 100 GeV, while from the intensity of the excess in all sky directions the shape of the halo could be reconstructed. The DM halo is consistent with an almost spherical isothermal profile with substructure in the Galactic plane in the form of toroidal rings at 4 and 14 kpc from the center. These rings lead to a peculiar shape of the rotation curve, in agreement with the data, which proves that the EGRET excess traces the Dark Matter