1,856 research outputs found
Summary of the CMS Discovery Potential for the MSSM SUSY Higgses
This work summarises the present understanding of the expected MSSM SUSY
Higgs reach for CMS. Many of the studies presented here result from detailed
detector simulations incorporating final CMS detector design and response. With
30 fb-1 the h -> gamma,gamma and h -> bb channels allow to cover most of the
MSSM parameter space. For the massive A,H,H+ MSSM Higgs states the channels A,H
-> tau,tau and H+ -> tau,nu turn out to be the most profitable ones in terms of
mass reach and parameter space coverage. Consequently CMS has made a big effort
to trigger efficiently on taus. Provided neutralinos and sleptons are not too
heavy, there is an interesting complementarity in the reaches for A,H ->
tau,tau and A,H -> chi,chi.Comment: 19 pages, 27 figure
The effect of magnetic impurities in a two-band superconductor: A point-contact study of Mn-substituted MgB2 single crystals
We present the first results of directional point-contact measurements in
Mg_{1-x}Mn_{x}B_2 single crystals, with x up to 0.015 and bulk T_c down to 13.3
K. The order parameters Delta_{sigma} and Delta_{pi} were obtained by fitting
the conductance curves with the two-band Blonder-Tinkham-Klapwijk (BTK) model.
Both Delta_{pi} and Delta_{sigma} decrease with the critical temperature of the
junctions T_c^A, but remain clearly distinct up to the highest Mn content. Once
analyzed within the Eliashberg theory, the results indicate that spin-flip
scattering is dominant in the sigma band, as also confirmed by first-principle
band structure calculations.Comment: 4 pages, 5 eps figures. New theoretical results added, text and some
figures changed. References adde
Cross-kink unpinning controls the medium- to high-temperature strength of body-centered cubic NbTiZr medium-entropy alloy
The deformation mechanisms of a NbTiZr body-centered cubic (BCC) medium-entropy alloy (MEA) are investigated by tensile testing at various temperatures. The yield strength (YS) shows a strong tempera- ture dependence from 77 K to 300 K, while being insensitive to temperatures between 300 K and 873 K, followed by a significant drop at 1073
Helicity detection of the astrophysical magnetic fields from radio emission statistics
We discuss inverse problem of detection turbulence magnetic field helical
properties using radio survey observations statistics. In this paper, we
present principal solution which connects magnetic helicity and correlation
between Faraday rotation measure and polarization degree of radio synchrotron
emission. The effect of depolarization plays the main role in this problem and
allows to detect magnetic helicity for certain frequency range of observable
radio emission. We show that the proposed method is mainly sensitive to a
large-scale magnetic field component.Comment: 5 pages, 6 figure
Logarithmic perturbation theory for radial Klein-Gordon equation with screened Coulomb potentials via expansions
The explicit semiclassical treatment of logarithmic perturbation theory for
the bound-state problem within the framework of the radial Klein-Gordon
equation with attractive real-analytic screened Coulomb potentials, contained
time-component of a Lorentz four-vector and a Lorentz-scalar term, is
developed. Based upon -expansions and suitable quantization conditions a
new procedure for deriving perturbation expansions is offered. Avoiding
disadvantages of the standard approach, new handy recursion formulae with the
same simple form both for ground and excited states have been obtained. As an
example, the perturbation expansions for the energy eigenvalues for the
Hulth\'en potential containing the vector part as well as the scalar component
are considered.Comment: 14 pages, to be submitted to Journal of Physics
The formation of Ti-O tetrahedra and band gap reduction in SiO2 via pulsed ion implantation
Titanium ions are implanted into amorphous SiO2 at two different fluences using pulsed ion implantation, and the resulting samples are annealed. Bulk sensitive soft X-ray absorption spectroscopy of the Ti L 2, 3 edge reveal strikingly different spectra for the two fluences. Spectral simulations using multiplet crystal field theory show clearly that for low fluence the Ti ions have a local octahedral coordination, while at higher fluence the formation of Ti4-O tetrahedra dominates. Using O K-edge X-ray absorption and emission, the effect of the Ti states on the valence and conduction bands of the host SiO2 is revealed. With the introduction of Ti tetrahedra, the band gap reduces from about 8 eV to just over 4 eV, due entirely to the Ti 3d conduction band states. These results demonstrate the possibility to obtain Ti-O tetrahedra in silica by Ti ion implantation and a suitable thermal treatment, clarify the mechanism of band gap reduction with Ti doping in SiO2, and demonstrate the sensitivity of L-edge X-ray absorption with a multiplet crystal field theory analysis to the Ti coordination of novel materials. © 2013 American Institute of Physics
Stochastic Acceleration in the Galactic Center HESS Source
Stochastic acceleration of electrons interacting resonantly with a turbulent
magnetic field in a small accretion torus appears to be the likely mechanism
responsible for much of Sagittarius A*'s millimeter and shorter wavelength
spectrum. The longer wavelength radiation is produced at larger radii by
electrons either diffusing from smaller scales or accelerated in situ. An
important prediction of this model is the ejection of a significant flux of
relativistic protons from a magnetic-field-dominated acceleration site into the
wind-shocked medium surrounding the black hole. Recently, several air Cerenkov
telescopes, notably HESS, have detected TeV emission from the Galactic center,
with characteristics hinting at a p-p-induced pion decay process for the
\gamma-ray emission. Given (1) the size of this acceleration region measured in
the radio band and (2) the wind-injected ISM mapped with Chandra using the
diffuse X-rays, it is feasible to test the idea that protons accelerated within
\~20 Schwarzschild radii of the black hole produce the TeV emission farther
out. We show a fraction of TeV protons scattering about once within ~3 pc of
Sagittarius A* and the proton power (~10^37 erg s^-1) produced in concert with
the 7 mm radio emission matches the TeV luminosity well. This model explains
why the TeV source does not vary on a timescale of a year or less. The particle
cascade generated by the p-p scatterings also produces bremsstrahlung, inverse
Compton, and synchrotron emission at longer wavelengths from secondary
particles. We compare these with current measurements and demonstrate that
GLAST will detect this source during its one-year all-sky survey.Comment: 19 pages, 3 figure
Refractory TaTiNb, TaTiNbZr, and TaTiNbZrX (X = Mo, W) high entropy alloys by combined use of high energy ball milling and spark plasma sintering: Structural characterization, mechanical properties, electrical resistivity, and thermal conductivity
Refractory TaTiNb, TaTiNbZr, and TaTiNbZrX (X = Mo, W) high entropy alloys were synthesized by combined use of high energy ball milling (HEBM) and spark plasma sintering (SPS). Powders of predominantly bcc TaTiNbZrX (X = Mo, W) refractory high entropy alloys (RHEAs) were successfully prepared by short-term HEBM (60 min) and then SPS-consolidated at 1373 K for 10 mi
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