109 research outputs found
Dark Matter in the Singlet Extension of MSSM: Explanation of Pamela and Implication on Higgs Phenomenology
As discussed recently by Hooper and Tait, the singlino-like dark matter in
the Minimal Supersymmetric Standard Model (MSSM) extended by a singlet Higgs
superfield can give a perfect explanation for both the relic density and the
Pamela result through the Sommerfeld-enhanced annihilation into singlet Higgs
bosons ( or followed by ) with being light enough to decay
dominantly to muons or electrons. In this work we analyze the parameter space
required by such a dark matter explanation and also consider the constraints
from the LEP experiments. We find that although the light singlet Higgs bosons
have small mixings with the Higgs doublets in the allowed parameter space,
their couplings with the SM-like Higgs boson (the lightest
doublet-dominant Higgs boson) can be enhanced by the soft parameter
and, in order to meet the stringent LEP constraints, the tends to
decay into the singlet Higgs pairs or instead of . So the
produced at the LHC will give a multi-muon signal, h_{SM} -> aa -> 4
muons or h_{SM} -> hh -> 4 a -> 8 muons.Comment: Version in JHE
Can MSSM with light sbottom and light gluino survive Z-peak constraints ?
In the framework of minimal supersymmetric model we examine the Z-peak
constraints on the scenario of one light sbottom (2--5.5 GeV) and light gluino
(12--16 GeV), which has been successfully used to explain the excess of bottom
quark production in hadron collision. Such a scenario is found to be severely
constrained by LEP Z-peak observables, especially by R_b, due to the large
effect of gluino-sbottom loops. To account for the R_b data in this scenario,
the other mass eigenstate of sbottom, i.e., the heavier one, must be lighter
than 125 (195) GeV at 2-sigma (3-sigma) level, which should have been produced
in association with the lighter one at LEP II and will probobaly be within the
reach of Tevatron Run 2.Comment: discussion on SUSY-EW effects added, to appear in PR
Loop effects and non-decoupling property of SUSY QCD in
One-loop SUSY QCD radiative correction to cross section is
calculated in the Minimal Supersymmetric Standard Model. We found that SUSY QCD
is non-decoupling if the gluino mass and the parameter , or
are at the same order and get large. The non-decoupling contribution can be
enhanced by large and therefore large corrections to the hadronic
production rates at the Tevatron and LHC are expected in the large
limit. The fundamental reason for such non-decoupling behavior is found to be
some couplings in the loops being proportional to SUSY mass parameters.Comment: 15 pages, 5 PS figures. A proof of non-decouplings of SUSY-QCD,
Comments on corresponding QCD correction and references adde
Probing Topcolor-Assisted Technicolor from Top-Charm Associated Production at LHC
We propose to probe the topcolor-assisted technicolor (TC2) model from the
top-charm associated productions at the LHC, which are highly suppressed in the
Standard Model. Due to the flavor-changing couplings of the top quark with the
scalars (top-pions and top-Higgs) in TC2 model, the top-charm associated
productions can occur via both the s-channel and t-channel parton processes by
exchanging a scalar field at the LHC. We examined these processes through Monte
Carlo simulation and found that they can reach the observable level at the LHC
in quite a large part of the parameter space of the TC2 model.Comment: Version to appear in PRD (Rapid Communication
Early Adverse Events, HPA Activity and Rostral Anterior Cingulate Volume in MDD
Prior studies have independently reported associations between major depressive disorder (MDD), elevated cortisol concentrations, early adverse events and region-specific decreases in grey matter volume, but the relationships among these variables are unclear. In the present study, we sought to evaluate the relationships between grey matter volume, early adverse events and cortisol levels in MDD.Grey matter volume was compared between 19 controls and 19 individuals with MDD using voxel-based morphometry. A history of early adverse events was assessed using the Childhood Trauma Questionnaire. Subjects also provided salivary cortisol samples. Depressed patients showed decreased grey matter volume in the rostral ACC as compared to controls. Rostral ACC volume was inversely correlated with both cortisol and early adverse events.These findings suggest a key relationship between ACC morphology, a history of early adverse events and circulating cortisol in the pathophysiology of MDD
Distributionally robust L1-estimation in multiple linear regression
Linear regression is one of the most important and widely used techniques in data analysis, for which a key step is the estimation of the unknown parameters. However, it is often carried out under the assumption that the full information of the error distribution is available. This is clearly unrealistic in practice. In this paper, we propose a distributionally robust formulation of L1-estimation (or the least absolute value estimation) problem, where the only knowledge on the error distribution is that it belongs to a well-defined ambiguity set. We then reformulate the estimation problem as a computationally tractable conic optimization problem by using duality theory. Finally, a numerical example is solved as a conic optimization problem to demonstrate the effectiveness of the proposed approach
Integrating Functional and Diffusion Magnetic Resonance Imaging for Analysis of Structure-Function Relationship in the Human Language Network
The capabilities of magnetic resonance imaging (MRI) to measure structural and functional connectivity in the human brain have motivated growing interest in characterizing the relationship between these measures in the distributed neural networks of the brain. In this study, we attempted an integration of structural and functional analyses of the human language circuits, including Wernicke's (WA), Broca's (BA) and supplementary motor area (SMA), using a combination of blood oxygen level dependent (BOLD) and diffusion tensor MRI.Functional connectivity was measured by low frequency inter-regional correlations of BOLD MRI signals acquired in a resting steady-state, and structural connectivity was measured by using adaptive fiber tracking with diffusion tensor MRI data. The results showed that different language pathways exhibited different structural and functional connectivity, indicating varying levels of inter-dependence in processing across regions. Along the path between BA and SMA, the fibers tracked generally formed a single bundle and the mean radius of the bundle was positively correlated with functional connectivity. However, fractional anisotropy was found not to be correlated with functional connectivity along paths connecting either BA and SMA or BA and WA. for use in diagnosing and determining disease progression and recovery
Study on the rare radiative decay in the standard model and multiscale walking technicolor model
Applying the perturbative QCD ( PQCD ) method, we study the decay
in the standard model and multiscale walking
technicolor model. In the SM, we find that the contribution of weak
annihilation is more important than that of the electromagnetic penguin. The
presence of Pseudo-Goldstone-Bosons in the MWTCM leads to a large enhancement
in the rate of , but this model is in conflict with
the branching ratio of ( ) and the CLEO data
on the branching ratio BR ( ). If topcolor is further
introduced, the calculated results in the topcolor assisted MWTCM can be
suppressed and be in agreement with the CLEO data for a certain range of the
parameters.Comment: 16 pages, Latex, no macros, 1 figure(in Latex), hard copy is
available upon request. to appear in Phys. Rev.
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