246 research outputs found
Dark Matter in the Left Right Twin Higgs Model
In the left-right twin Higgs model, one of the neutral Higgses is a natural
candidate for WIMP dark matter. We analyzed the dark matter relic density in
this framework and identified regions of parameter space that provide the right
amount of dark matter. We also studied the dark matter in the more general
inert Higgs doublet model in which the mass splittings between the dark matter
and other particles do not follow the relations in the left-right twin Higgs
model.Comment: 18 page
Phenomenology of The Left-Right Twin Higgs Model
The twin Higgs mechanism has recently been proposed to solve the little
hierarchy problem. We study the implementation of the twin Higgs mechanism in
left-right models. At TeV scale, heavy quark and gauge bosons appear, with rich
collider phenomenology. In addition, there are extra Higgses, some of which
couple to both the Standard Model fermion sector and the gauge sector, while
others couple to the gauge bosons only. We present the particle spectrum, and
study the general features of the collider phenomenology of this class of model
at the Large Hadron Collider.Comment: 41 pages, version appears in PR
Variation of the cross section for e+e- --> W+H- in the Minimal Supersymmetric Standard Model
We study the loop-induced process e+e- --> W+H- in the Minimal Supersymmetric
Standard Model (MSSM). This process allows the charged Higgs boson to be
produced in e+e- collisions when its mass is larger than half the
center-of-mass energy, so that e+e- --> H+H- is kinematically forbidden. By
scanning over the MSSM parameters subject to experimental constraints we
examine the range of values possible for this cross section. We find that, in
regions of parameter space where this cross section is large enough to be of
interest, the contributions from supersymmetric particles typically increase
the cross section by 50-100% compared to the non-supersymmetric two Higgs
doublet model result. Choosing a few typical MSSM parameter sets, we show the
regions in the m_{H^{\pm}}-tan(beta) plane in which at least 10 W^{\pm}H^{\mp}
events would be produced at the e+e- collider for m_{H^{\pm}} >= sqrt(s)/2. We
also show that including radiative corrections to the MSSM Higgs sector has
only a small effect on the cross section.Comment: 5 pages, 4 figures, v2: minor changes; v3: extensive changes to text
and figures, version to appear in PR
Florbetapir positron emission tomography and cerebrospinal fluid biomarkers
BACKGROUND:
We evaluated the relationship between florbetapir-F18 positron emission tomography (FBP PET) and cerebrospinal fluid (CSF) biomarkers.
METHODS:
Alzheimer's Disease Neuroimaging Initiative-Grand Opportunity and Alzheimer's Disease Neuroimaging Initiative 2 (GO/2) healthy control (HC), mild cognitive impairment (MCI), and Alzheimer's disease (AD) dementia subjects with clinical measures and CSF collected ±90 days of FBP PET data were analyzed using correlation and logistic regression.
RESULTS:
In HC and MCI subjects, FBP PET anterior and posterior cingulate and composite standard uptake value ratios correlated with CSF amyloid beta (Aβ1-42) and tau/Aβ1-42 ratios. Using logistic regression, Aβ1-42, total tau (t-tau), phosphorylated tau181P (p-tau), and FBP PET composite each differentiated HC versus AD. Aβ1-42 and t-tau distinguished MCI versus AD, without additional contribution by FBP PET. Total tau and p-tau added discriminative power to FBP PET when classifying HC versus AD.
CONCLUSION:
Based on cross-sectional diagnostic groups, both amyloid and tau measures distinguish healthy from demented subjects. Longitudinal analyses are needed
Extra Families, Higgs Spectrum and Oblique Corrections
The standard model accommodates, but does not explain, three families of
leptons and quarks, while various extensions suggest extra matter families. The
oblique corrections from extra chiral families with relatively light
(weak-scale) masses, , are analyzed and used to constrain the
number of extra families and their spectrum. The analysis is motivated, in
part, by recent N = 2 supersymmetry constructions, but is performed in a
model-independent way. It is shown that the correlations among the
contributions to the three oblique parameters, rather than the contribution to
a particular one, provide the most significant bound. Nevertheless, a single
extra chiral family with a constrained spectrum is found to be consistent with
precision data without requiring any other new physics source. Models with
three additional families may also be accommodated but only by invoking
additional new physics, most notably, a two-Higgs-doublet extension. The
interplay between the spectra of the extra fermions and the Higgs boson(s) is
analyzed in the case of either one or two Higgs doublets, and its implications
are explored. In particular, the precision bound on the SM-like Higgs boson
mass is shown to be significantly relaxed in the presence of an extra
relatively light chiral family.Comment: 20 pages, 8 figures, version for PR
Associated production of H^{\pm} and W^{\mp} in high-energy e+e- collisions in the Minimal Supersymmetric Standard Model
We study the associated production of the charged Higgs boson and W^{\pm}
gauge boson in high energy e+e- collisions in the Minimal Supersymmetric
Standard Model (MSSM). This associated production, which first arises at the
one loop level, offers the possibility of producing the charged Higgs boson at
the e+e- collider with mass more than half the center-of-mass energy, when the
charged Higgs pair production is kinematically forbidden. We present analytic
and numerical results for the cross section for e+e- --> W+ H- in the full
MSSM, taking into account the previously uncalculated contributions from
supersymmetric (SUSY) particles. We find that the contributions of the SUSY
particles enhance the cross section over most of SUSY parameter space,
especially when the SUSY particles are light, ~200 GeV. With favorable SUSY
parameters, at small tan beta, this process can yield more than ten
W^{\pm}H^{\mp} events for m_{H^{\pm}} <~ 350 GeV in 500 fb-1 at a 500 GeV e+e-
collider, or m_{H^{\pm}} <~ 600 GeV in 1000 fb-1 at a 1000 GeV collider. 80%
left-handed polarization of the e- beam improves these reaches to m_{H^{\pm}}
<~ 375 GeV and m_{H^{\pm}} <~ 670 GeV, respectively.Comment: v2: 21 pages, 9 figures, comments on Higgs search bounds and new
references added, and minor changes; v3: 23 pages, 11 figures, review of
literature moved from introduction to new Sec.5 and 2 plots added, references
added, typos corrected; v4: bug fixed in nu nubar H0 cross section (Fig.11),
version to appear in PR
Folyóirat vagy gyűjteményes kötet? (Csokonai Diétai Magyar Múzsája)
BACKGROUND: The complex interplay between viral replication and host immune response during infection remains poorly understood. While many viruses are known to employ anti-immune strategies to facilitate their replication, highly pathogenic virus infections can also cause an excessive immune response that exacerbates, rather than reduces pathogenicity. To investigate this dichotomy in severe acute respiratory syndrome coronavirus (SARS-CoV), we developed a transcriptional network model of SARS-CoV infection in mice and used the model to prioritize candidate regulatory targets for further investigation. RESULTS: We validated our predictions in 18 different knockout (KO) mouse strains, showing that network topology provides significant predictive power to identify genes that are important for viral infection. We identified a novel player in the immune response to virus infection, Kepi, an inhibitory subunit of the protein phosphatase 1 (PP1) complex, which protects against SARS-CoV pathogenesis. We also found that receptors for the proinflammatory cytokine tumor necrosis factor alpha (TNFα) promote pathogenesis, presumably through excessive inflammation. CONCLUSIONS: The current study provides validation of network modeling approaches for identifying important players in virus infection pathogenesis, and a step forward in understanding the host response to an important infectious disease. The results presented here suggest the role of Kepi in the host response to SARS-CoV, as well as inflammatory activity driving pathogenesis through TNFα signaling in SARS-CoV infections. Though we have reported the utility of this approach in bacterial and cell culture studies previously, this is the first comprehensive study to confirm that network topology can be used to predict phenotypes in mice with experimental validation
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