29,109 research outputs found
New approach to determine proton-nucleus interactions from experimental bremsstrahlung data
A new approach is presented to determine the proton-nucleus interactions from
the analysis of the accompanying photon bremsstrahlung. We study the scattering
of at the proton incident energies of 140 and 145~MeV, and
the scattering of , ,
and at the proton incident energy of 190~MeV. The model
determines contributions of the coherent emission (formed by an interaction
between the scattering proton and nucleus as a whole without the internal
many-nucleon structure), incoherent emission (formed by interactions between
the scattering proton and nucleus with the internal many-nucleon structure),
and transition between them in dependence on the photon energy. The
radius-parameter of the proton-nucleus potential for these reactions is
extracted from the experimental bremsstrahlung data analysis. We explain the
hump-shaped plateau in the intermediate- and high-energy regions of the spectra
by the essential presence of the incoherent emission, while at low energies the
coherent emission predominates which produces the logarithmic shape spectrum.
We provide our predictions (in absolute scale) for the angular distribution of
the bremsstrahlung photons in order to test our model, results and analysis in
further experiments.Comment: 25 pages, 8 figure
Quantum design using a multiple internal reflections method in a study of fusion processes in the capture of alpha-particles by nuclei
A high precision method to determine fusion in the capture of
-particles by nuclei is presented. For -capture by and , such an approach gives (1) the parameters of the
--nucleus potential and (2) fusion probabilities. This method found new
parametrization and fusion probabilities and decreased the error by
times for and times for in a description of experimental data in comparison with existing results.
We show that the sharp angular momentum cutoff proposed by Glas and Mosel is a
rough approximation, Wong's formula and the Hill-Wheeler approach determine the
penetrability of the barrier without a correct consideration of the barrier
shape, and the WKB approach gives reduced fusion probabilities. Based on our
fusion probability formula, we explain the difference between experimental
cross-sections for and , which
is connected with the theory of coexistence of the spherical and deformed
shapes in the ground state for nuclei near the neutron magic shell . To
provide deeper insight into the physics of nuclei with the new magic number
, the cross-section for is predicted for future
experimental tests. The role of nuclear deformations in calculations of the
fusion probabilities is analyzed.Comment: 46 pages, 23 figure
The effect of non-linear quantum electrodynamics on relativistic transparency and laser absorption in ultra-relativistic plasmas
With the aid of large-scale three-dimensional QED-PIC simulations, we
describe a realistic experimental configuration to measure collective effects
that couple strong field quantum electrodynamics to plasma kinetics. For two
counter propagating lasers interacting with a foil at intensities exceeding
Wcm, a binary result occurs; when quantum effects are
included, a foil that classically would effectively transmit the laser pulse
becomes opaque. This is a dramatic change in plasma behavior, directly as a
consequence of the coupling of radiation reaction and pair production to plasma
dynamics
Manifestation of important role of nuclear forces in emission of photons in scattering of pions off nuclei
Bremsstrahlung of photons emitted during the scattering of -mesons
off nuclei is studied for the first time. Role of interactions between
-mesons and nuclei in the formation of the bremsstrahlung emission is
analyzed in details. We discover essential contribution of emitted photons from
nuclear part of Johnson-Satchler potential to the full spectrum, in contrast to
the optical Woods-Saxon potential. We observe unusual essential influence of
the nuclear part of both potentials on the spectrum at high photon energies.
This phenomenon opens a new experimental way to study and check non-Coulomb and
nuclear interactions between pions and nuclei via measurements of the emitted
photons. We provide predictions of the bremsstrahlung spectra for pion
scattering off .Comment: 14 pages, 3 figure
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