583 research outputs found
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
Relic Neutralino Densities and Detection Rates with Nonuniversal Gaugino Masses
We extend previous analyses on the interplay between nonuniversalities in the
gaugino mass sector and the thermal relic densities of LSP neutralinos, in
particular to the case of moderate to large tan beta. We introduce a set of
parameters that generalizes the standard unified scenario to cover the complete
allowed parameter space in the gaugino mass sector. We discuss the physical
significance of the cosmologically preferred degree of degeneracy between
charginos and the LSP and study the effect this degree of degeneracy has on the
prospects for direct detection of relic neutralinos in the next round of dark
matter detection experiments. Lastly, we compare the fine tuning required to
achieve a satisfactory relic density with the case of universal gaugino masses,
as in minimal supergravity, and find it to be of a similar magnitude. The
sensitivity of quantifiable measures of fine-tuning on such factors as the
gluino mass and top and bottom masses is also examined.Comment: Uses RevTeX; 14 pages, 16 figure
Phenomenological Implications of Deflected Mirage Mediation: Comparison with Mirage Mediation
We compare the collider phenomenology of mirage mediation and deflected
mirage mediation, which are two recently proposed "mixed" supersymmetry
breaking scenarios motivated from string compactifications. The scenarios
differ in that deflected mirage mediation includes contributions from gauge
mediation in addition to the contributions from gravity mediation and anomaly
mediation also present in mirage mediation. The threshold effects from gauge
mediation can drastically alter the low energy spectrum from that of pure
mirage mediation models, resulting in some cases in a squeezed gaugino spectrum
and a gluino that is much lighter than other colored superpartners. We provide
several benchmark deflected mirage mediation models and construct model lines
as a function of the gauge mediation contributions, and discuss their discovery
potential at the LHC.Comment: 29 pages, 9 figure
TeV Symmetry and the Little Hierarchy Problem
Constraints from precision electroweak measurements reveal no evidence for
new physics up to 5 - 7 TeV, whereas naturalness requires new particles at
around 1 TeV to address the stability of the electroweak scale. We show that
this "little hierarchy problem" can be cured by introducing a symmetry for new
particles at the TeV scale. As an example, we construct a little Higgs model
with this new symmetry, dubbed T-parity, which naturally solves the little
hierarchy problem and, at the same time, stabilize the electroweak scale up to
10 TeV. The model has many important phenomenological consequences, including
consistency with the precision data without any fine-tuning, a stable
weakly-interacting particle as the dark matter candidate, as well as collider
signals completely different from existing little Higgs models, but rather
similar to the supersymmetric theories with conserved R-parity.Comment: 15 pages, 1 figure; v.2: typos corrected and various minor
modifications/expansions on the presentations. now 16 pages and 1 figure.
version to appear on JHE
uPARAP/Endo180 is essential for cellular uptake of collagen and promotes fibroblast collagen adhesion
The uptake and lysosomal degradation of collagen by fibroblasts constitute a major pathway in the turnover of connective tissue. However, the molecular mechanisms governing this pathway are poorly understood. Here, we show that the urokinase plasminogen activator receptor–associated protein (uPARAP)/Endo180, a novel mesenchymally expressed member of the macrophage mannose receptor family of endocytic receptors, is a key player in this process. Fibroblasts from mice with a targeted deletion in the uPARAP/Endo180 gene displayed a near to complete abrogation of collagen endocytosis. Furthermore, these cells had diminished initial adhesion to a range of different collagens, as well as impaired migration on fibrillar collagen. These studies identify a central function of uPARAP/Endo180 in cellular collagen interactions
Direct detection of neutralino dark matter in supergravity
The direct detection of neutralino dark matter is analysed in general
supergravity scenarios, where non-universal soft scalar and gaugino masses can
be present. In particular, the theoretical predictions for the
neutralino-nucleon cross section are studied and compared with the sensitivity
of dark matter detectors. We take into account the most recent astrophysical
and experimental constraints on the parameter space, including the current
limit on B(Bs-> mu+ mu-). The latter puts severe limitations on the dark matter
scattering cross section, ruling out most of the regions that would be within
the reach of present experiments. We show how this constraint can be softened
with the help of appropriate choices of non-universal parameters which increase
the Higgsino composition of the lightest neutralino and minimise the chargino
contribution to the b->s transition.Comment: 27 pages, 22 figure
Activation and localization of matrix metalloproteinase-2 and -9 in the skeletal muscle of the muscular dystrophy dog (CXMDJ)
<p>Abstract</p> <p>Background</p> <p>Matrix metalloproteinases (MMPs) are key regulatory molecules in the formation, remodeling and degradation of all extracellular matrix (ECM) components in both physiological and pathological processes in various tissues. The aim of this study was to examine the involvement of gelatinase MMP family members, MMP-2 and MMP-9, in dystrophin-deficient skeletal muscle. Towards this aim, we made use of the canine X-linked muscular dystrophy in Japan (CXMD<sub>J</sub>) model, a suitable animal model for Duchenne muscular dystrophy.</p> <p>Methods</p> <p>We used surgically biopsied tibialis cranialis muscles of normal male dogs (n = 3) and CXMD<sub>J </sub>dogs (n = 3) at 4, 5 and 6 months of age. Muscle sections were analyzed by conventional morphological methods and <it>in situ </it>zymography to identify the localization of MMP-2 and MMP-9. MMP-2 and MMP-9 activity was examined by gelatin zymography and the levels of the respective mRNAs in addition to those of regulatory molecules, including MT1-MMP, TIMP-1, TIMP-2, and RECK, were analyzed by semi-quantitative RT-PCR.</p> <p>Results</p> <p>In CXMD<sub>J </sub>skeletal muscle, multiple foci of both degenerating and regenerating muscle fibers were associated with gelatinolytic MMP activity derived from MMP-2 and/or MMP-9. In CXMD<sub>J </sub>muscle, MMP-9 immunoreactivity localized to degenerated fibers with inflammatory cells. Weak and disconnected immunoreactivity of basal lamina components was seen in MMP-9-immunoreactive necrotic fibers of CXMD<sub>J </sub>muscle. Gelatinolytic MMP activity observed in the endomysium of groups of regenerating fibers in CXMD<sub>J </sub>did not co-localize with MMP-9 immunoreactivity, suggesting that it was due to the presence of MMP-2. We observed increased activities of pro MMP-2, MMP-2 and pro MMP-9, and levels of the mRNAs encoding MMP-2, MMP-9 and the regulatory molecules, MT1-MMP, TIMP-1, TIMP-2, and RECK in the skeletal muscle of CXMD<sub>J </sub>dogs compared to the levels observed in normal controls.</p> <p>Conclusion</p> <p>MMP-2 and MMP-9 are likely involved in the pathology of dystrophin-deficient skeletal muscle. MMP-9 may be involved predominantly in the inflammatory process during muscle degeneration. In contrast, MMP-2, which was activated in the endomysium of groups of regenerating fibers, may be associated with ECM remodeling during muscle regeneration and fiber growth.</p
MT1-matrix metalloproteinase directs arterial wall invasion and neointima formation by vascular smooth muscle cells
During pathologic vessel remodeling, vascular smooth muscle cells (VSMCs) embedded within the collagen-rich matrix of the artery wall mobilize uncharacterized proteolytic systems to infiltrate the subendothelial space and generate neointimal lesions. Although the VSMC-derived serine proteinases, plasminogen activator and plasminogen, the cysteine proteinases, cathepsins L, S, and K, and the matrix metalloproteinases MMP-2 and MMP-9 have each been linked to pathologic matrix-remodeling states in vitro and in vivo, the role that these or other proteinases play in allowing VSMCs to negotiate the three-dimensional (3-D) cross-linked extracellular matrix of the arterial wall remains undefined. Herein, we demonstrate that VSMCs proteolytically remodel and invade collagenous barriers independently of plasmin, cathepsins L, S, or K, MMP-2, or MMP-9. Instead, we identify the membrane-anchored matrix metalloproteinase, MT1-MMP, as the key pericellular collagenolysin that controls the ability of VSMCs to degrade and infiltrate 3-D barriers of interstitial collagen, including the arterial wall. Furthermore, genetic deletion of the proteinase affords mice with a protected status against neointimal hyperplasia and lumen narrowing in vivo. These studies suggest that therapeutic interventions designed to target MT1-MMP could prove beneficial in a range of human vascular disease states associated with the destructive remodeling of the vessel wall extracellular matrix
T-parity, its problems and their solution
We point out a basic difficulty in the construction of little-Higgs models
with T-parity which is overlooked by large part of the present literature.
Almost all models proposed so far fail to achieve their goal: they either
suffer from sizable electroweak corrections or from a breakdown of collective
breaking. We provide a model building recipe to bypass the above problem and
apply it to build the simplest T-invariant extension of the Littlest Higgs. Our
model predicts additional T-odd pseudo-Goldstone bosons with weak scale masses.Comment: 25 pages, 2 appendice
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