2,017 research outputs found
Natural Supersymmetry and Implications for Higgs physics
We re-analyze the LHC bounds on light third generation squarks in Natural
Supersymmetry, where the sparticles have masses inversely proportional to their
leading-log contributions to the electroweak symmetry breaking scale. Higgsinos
are the lightest supersymmetric particles; top and bottom squarks are the
next-to-lightest sparticles that decay into both neutral and charged Higgsinos
with well-defined branching ratios determined by Yukawa couplings and
kinematics. The Higgsinos are nearly degenerate in mass, once the bino and wino
masses are taken to their natural (heavy) values. We consider three scenarios
for the stop and sbottom masses: (I) is light, (II)
and are light, and (III) , , and
are light. Dedicated stop searches are currently sensitive to
Scenarios II and III, but not Scenario I. Sbottom-motivated searches () impact both squark flavors due to \tilde{t} \ra b \charp_1 as well
as \tilde{b} \ra b \neut_{1,2}, constraining Scenarios I and III with
somewhat weaker constraints on Scenario II. The totality of these searches
yield relatively strong constraints on Natural Supersymmetry. Two regions that
remain are: (1) the "compressed wedge", where , and (2) the "kinematic limit" region, where
m_{\tilde{q}} \gsim 600-750 GeV, at the kinematic limit of the LHC searches.
We calculate the correlated predictions for Higgs physics, demonstrating that
these regions lead to distinct predictions for the lightest Higgs couplings
that are separable with \simeq 10% measurements. We show that these
conclusions remain largely unchanged once the MSSM is extended to the NMSSM in
order to naturally obtain a large enough mass for the lightest Higgs boson
consistent with LHC data.Comment: 18 pages, 8 figure
Adjusted Empirical Likelihood for Long-memory Time Series Models
Empirical likelihood method has been applied to short-memory time series
models by Monti (1997) through the Whittle's estimation method. Yau (2012)
extended this idea to long-memory time series models. Asymptotic distributions
of the empirical likelihood ratio statistic for short and long-memory time
series have been derived to construct confidence regions for the corresponding
model parameters. However, computing profile empirical likelihood function
involving constrained maximization does not always have a solution which leads
to several drawbacks. In this paper, we propose an adjusted empirical
likelihood procedure to modify the one proposed by Yau (2012) for
autoregressive fractionally integrated moving average (ARFIMA) model. It
guarantees the existence of a solution to the required maximization problem as
well as maintains same asymptotic properties obtained by Yau (2012).
Simulations have been carried out to illustrate that the adjusted empirical
likelihood method for different long-time series models provides better
confidence regions and coverage probabilities than the unadjusted ones,
especially for small sample sizes
Quasi-equilibrium optical nonlinearities in spin-polarized GaAs
Semiconductor Bloch equations, which microscopically describe the dynamics of
a Coulomb interacting, spin-unpolarized electron-hole plasma, can be solved in
two limits: the coherent and the quasi-equilibrium regime. These equations have
been recently extended to include the spin degree of freedom, and used to
explain spin dynamics in the coherent regime. In the quasi-equilibrium limit,
one solves the Bethe-Salpeter equation in a two-band model to describe how
optical absorption is affected by Coulomb interactions within a
spin-unpolarized plasma of arbitrary density. In this work, we modified the
solution of the Bethe-Salpeter equation to include spin-polarization and light
holes in a three-band model, which allowed us to account for spin-polarized
versions of many-body effects in absorption. The calculated absorption
reproduced the spin-dependent, density-dependent and spectral trends observed
in bulk GaAs at room temperature, in a recent pump-probe experiment with
circularly polarized light. Hence our results may be useful in the microscopic
modelling of density-dependent optical nonlinearities in spin-polarized
semiconductors.Comment: 7 pages, 6 figure
Hypertension Treatment for Patients with Advanced Chronic Kidney Disease
Chronic kidney disease is common and frequently complicated with hypertension. As a major modifiable risk factor for cardiovascular disease in this high risk population, treatment of hypertension in chronic kidney disease is of paramount importance. We review the epidemiology and pathogenesis of hypertension in chronic kidney disease and then update the latest study results for treatment including salt restriction, invasive endovascular procedures, and pharmacologic therapy. Recent trials draw into question the efficacy of renal artery stenting or renal denervation for hypertension in chronic kidney disease, as well as renin-angiotensin-aldosterone system blockade as first line therapy of hypertension in end stage renal disease. Positive trial results reemphasize salt restriction and challenge the prevailing prejudice against the use of thiazide-like diuretics in advanced chronic kidney disease. Lastly, clinical practice guidelines are trending away from recommending tight blood pressure control in chronic kidney disease
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