28,775 research outputs found
A comparative study for structural and electronic properties of single-crystal ScN
A comparative study by FP-LAPW calculations based on DFT within LDA, PBE-GGA,
EV-PW-GGA, and EV-GGA-LDA schemes is introduced for
the structural and electronic properties of ScN in RS, ZB, WZ, and CsCl phases.
According to all approximations used in this work, the RS phase is the stable
ground state structure and makes a transition to CsCl phase at high transition
pressure. While PBE-GGA and EV-PW-GGA's have provided better
structural features such as equilibrium lattice constant and bulk modulus, only
EV-PW-GGA and EV-GGA-LDA's have given the non zero,
positive indirect energy gap for RS-ScN, comparable with the experimental ones.
The indirect band gap of ScN in RS phase is enlarged to the corresponding
measured value by EV-PW-GGA+U calculations in which the
Coulomb self and exchange-correlation interactions of the localized d-orbitals
of Sc have been corrected by the potential parameter of U. The
EV-PW-GGA calculations have also provided good results for the
structural and electronic features of ScN in ZB, WZ, and CsCl phases comparable
with the theoretical data available in the literature. EV-PW-GGA
and EV-PW-GGA+U schemes are considered to be the best
ones among the others when the structural and electronic features of ScN are
aimed to be calculated by the same exchange-correlation energy approximations.Comment: 13 pages, 8 figure
Charged Higgs production from polarized top-quark decay in the 2HDM considering the general-mass variable-flavor-number scheme
Charged Higgs bosons are predicted by some non-minimal Higgs
scenarios, such as models containing Higgs triplets and two-Higgs-doublet
models, so that the experimental observation of these bosons would indicate
physics beyond the Standard Model. In the present work, we introduce a new
channel to indirect search for the charged Higgses through the hadronic decay
of polarized top quarks where a top quark decays into a charged Higgs and
a bottom-flavored hadron via the hadronization process of the produced
bottom quark, . To obtain the energy
spectrum of produced -hadrons we present, for the first time, an analytical
expression for the corrections to the differential decay
width of the process in the presence of a massive b-quark
in the General-Mass Variable-Flavor-Number Scheme (GM-VFNS). We find that the
most reliable predictions for the B-hadron energy spectrum are made in the
GM-VFN scheme, specifically, when the Type-II 2HDM scenario is concerned
Next-to-leading order corrections to the spin-dependent energy spectrum of hadrons from polarized top quark decay in the general two Higgs doublet model
In recent years, searches for the light and heavy charged Higgs bosons have
been done by the ATLAS and the CMS collaborations at the Large Hadron Collider
(LHC) in proton-proton collision. Nevertheless, a definitive search is a
program that still has to be carried out at the LHC. The experimental
observation of charged Higgs bosons would indicate physics beyond the Standard
Model. In the present work, we study the scaled-energy distribution of
bottom-flavored mesons () inclusively produced in polarized top quark decays
into a light charged Higgs boson and a massless bottom quark at next-to-leading
order in the two-Higgs-doublet model; . This
spin-dependent energy distribution is studied in a specific helicity coordinate
system where the polarization vector of the top quark is measured with respect
to the direction of the Higgs momentum. The study of these energy distributions
could be considered as a new channel to search for the charged Higgs bosons at
the LHC. For our numerical analysis and phenomenological predictions, we
restrict ourselves to the unexcluded regions of the MSSM
parameter space determined by the recent results of the CMS \cite{CMS:2014cdp}
and ATLAS \cite{TheATLAScollaboration:2013wia} collaborations.Comment: 10 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1611.0801
All-dielectric reciprocal bianisotropic nanoparticles
The study of high-index dielectric nanoparticles currently attracts a lot of
attention. They do not suffer from absorption but promise to provide control on
the properties of light comparable to plasmonic nanoparticles. To further
advance the field, it is important to identify versatile dielectric
nanoparticles with unconventional properties. Here, we show that breaking the
symmetry of an all-dielectric nanoparticle leads to a geometrically tunable
magneto-electric coupling, i.e. an omega-type bianisotropy. The suggested
nanoparticle exhibits different backscatterings and, as an interesting
consequence, different optical scattering forces for opposite illumination
directions. An array of such nanoparticles provides different reflection phases
when illuminated from opposite directions. With a proper geometrical tuning,
this bianisotropic nanoparticle is capable of providing a phase change
in the reflection spectrum while possessing a rather large and constant
amplitude. This allows creating reflectarrays with near-perfect transmission
out of the resonance band due to the absence of an usually employed metallic
screen.Comment: 7 pages, 6 figure
Lagrangian tracer dynamics in a closed cylindrical turbulent convection cell
Turbulent Rayleigh-Benard convection in a closed cylindrical cell is studied
in the Lagrangian frame of reference with the help of three-dimensional direct
numerical simulations. The aspect ratio of the cell Gamma is varied between 1
and 12, and the Rayleigh number Ra between 10^7 and 10^9. The Prandtl number Pr
is fixed at 0.7. It is found that both the pair dispersion of the Lagrangian
tracer particles and the statistics of the acceleration components measured
along the particle trajectories depend on the aspect ratio for a fixed Rayleigh
number for the parameter range covered in our studies. This suggests that
large-scale circulations present in the convection cell affect the Lagrangian
dynamics. Our findings are in qualitative agreement with existing Lagrangian
laboratory experiments on turbulent convection.Comment: 10 pages, 11 Postscript figure
Derivation of the Lamb Shift using an Effective Field Theory
We rederive the shift of the hydrogen levels in the non-recoil
() limit using Nonrelativistic QED (NRQED), an effective field
theory developed by Caswell and Lepage (Phys. Lett. 167B, 437 (1986)). Our
result contains the Lamb shift as a special case. Our calculation is far
simpler than traditional approaches and has the advantage of being systematic.
It also clearly illustrates the need to renormalize (or ``match'') the
coefficients of the effective theory beyond tree level.Comment: 15 pages, 11 Postscript figures, uses Latex2e and epsf.te
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