40 research outputs found
Channeling and radiation of the 855 MeV electrons enhanced by the re-channeling in a periodically bent diamond crystal
Channeling properties and radiation spectra are studied on the grounds of
numerical simulations for the 855 MeV electrons in a periodically bent diamond
crystal. The bent crystalline profiles are shown to enhance the re-channeling
of the projectiles and to produce distinct lines in the radiation spectra. The
results obtained are analyzed and contrasted to the properties of the planar
channeling and of the channeling in uniformly bent crystals.Comment: 8 pages, 5 figure
Neutrino-electron processes in a dense maqnetized plasma
The neutrino-electron processes in a dense strongly degenerate magnetized
plasma are analyzed in the framework of the Standard Model. The total
probability and the mean values of the neutrino energy and momentum losses are
calculated. It is shown that neutrino scattering on the excited electrons with
Landau level number conservation dominates under the conditions "mu^2 > eB >>
mu T" but does not give a contribution into the neutrino force acting on plasma
along the magnetic field.Comment: 7 pages, LATEX, to appear in Modern Physics Letters
Simulation of Ultra-Relativistic Electrons and Positrons Channeling in Crystals with MBN Explorer
A newly developed code, implemented as a part of the \MBNExplorer package
\cite{MBN_ExplorerPaper,MBN_ExplorerSite} to simulate trajectories of an
ultra-relativistic projectile in a crystalline medium, is presented. The motion
of a projectile is treated classically by integrating the relativistic
equations of motion with account for the interaction between the projectile and
crystal atoms. The probabilistic element is introduced by a random choice of
transverse coordinates and velocities of the projectile at the crystal entrance
as well as by accounting for the random positions of the atoms due to thermal
vibrations. The simulated trajectories are used for numerical analysis of the
emitted radiation. Initial approbation and verification of the code have been
carried out by simulating the trajectories and calculating the radiation
emitted by \E=6.7 GeV and \E=855 MeV electrons and positrons in oriented
Si(110) crystal and in amorphous silicon. The calculated spectra are compared
with the experimental data and with predictions of the Bethe-Heitler theory for
the amorphous environment.Comment: 41 pages, 11 figures. Initially submitted on Dec 29, 2012 to Phys.
Rev.
Fine structure of the exciton absorption in semiconductor superlattices in crossed electric and magnetic fields
The exciton absorption coefficient is determined analytically for a
semiconductor superlattice in crossed electric and magnetic fields, for the
magnetic field being parallel and the electric field being perpendicular to the
superlattice axis. Our investigation applies to the case where the magnetic
length, while being much smaller than the exiton Bohr radius, considerably
exceeds the superlattice period. The optical absorption in superlattices
displays a spectral fine structure related to the sequences of exciton states
bound whose energies are adjacent to the Landau energies of the charge carriers
in the magnetic field. We study effects of external fields and of the
centre-of-mass exciton motion on the fine structure peak positions and
oscillator strengths. In particular, we find that the inversion of the
orientation of the external fields and of the in-plane total exciton momentum
notably affects the absorption spectrum. Conditions for the experimental
observation of the exciton absorption are discussed
Neutrino-electron scattering in dense magnetized plasma
We derive exact expressions for the cross section of neutrino scattering on
electrons in dense, hot stellar matter, in the presence of strong magnetic
fields. Numerical calculations of the scattering cross sections at various
densities, temperatures and magnetic fields, are performed. Strong, quantizing
magnetic fields modify significantly the angular and energy dependence of the
scattering cross section.Comment: Physical Review D, to be published, 18 pages, using REVTEX, without
figures. Figures (hardcopy) available upon request from one of the authors
([email protected]
Neutrino opacity in magnetised hot and dense nuclear matter
We study the neutrino interaction rates in hot matter at high densities in
the presence of uniform magnetic field. The neutrino cross-sections involving
both the charged current absorption and neutral current scattering reactions on
baryons and leptons have been considered. We have in particular considered the
interesting case when the magnetic field is strong enough to completely
polarise the protons and electrons in supernovae and neutron stars. The opacity
in such a situation is considerably modified and the cross-section develops
anisotropy. This has implications for phenomenon invoked in the literature to
explain the observed pulsar kicks.Comment: 22 latex pages and 7 postscript figure