21,388 research outputs found
Deuteron-deuteron scattering above four-nucleon breakup threshold
Deuteron-deuteron elastic scattering and transfer reactions in the energy
regime above four-nucleon breakup threshold are described by solving exact
four-particle equations for transition operators. Several realistic nuclear
interaction models are used, including the one with effective many-nucleon
forces generated by the explicit -isobar excitation; the Coulomb force
between protons is taken into account as well. Differential cross sections,
deuteron analyzing powers, outgoing nucleon polarization, and
deuteron-to-neutron polarization transfer coefficients are calculated at 10 MeV
deuteron energy. Overall good agreement with the experimental data is found.
The importance of breakup channels is demonstrated.Comment: 5 figure
Four-body calculation of elastic deuteron-deuteron scattering
Fully converged calculations of deuteron-deuteron elastic scattering
observables are performed at energies above three- and four-body breakup
threshold. Differential cross sections and analyzing powers are obtained using
realistic nucleon-nucleon force models together with the Coulomb repulsion
between protons. For all observables we find a very reasonable agreement with
the available experimental data limited to deuteron beam energies up to 25.3
MeV.Comment: 5 figures, to be published in Phys. Rev.
Calculation of neutron-He scattering up to 30 MeV
Microscopic calculations of four-body collisions become very challenging in
the energy regime above the threshold for four free particles. The
neutron-He scattering is an example of such process with elastic,
rearrangement, and breakup channels. We aim to calculate observables for
elastic and inelastic neutron-He reactions up to 30 MeV neutron energy
using realistic nuclear force models. We solve the Alt, Grassberger, and
Sandhas (AGS) equations for the four-nucleon transition operators in the
momentum-space framework. The complex-energy method with special integration
weights is applied to deal with the complicated singularities in the kernel of
AGS equations. We obtain fully converged results for the differential cross
section and neutron analyzing power in the neutron-He elastic scattering
as well as the total cross sections for inelastic reactions. Several realistic
potentials are used, including the one with an explicit isobar
excitation. There is reasonable agreement between the theoretical predictions
and experimental data for the neutron-He scattering in the considered
energy regime. The most remarkable disagreements are seen around the minimum of
the differential cross section and the extrema of the neutron analyzing power.
The breakup cross section increases with energy exceeding rearrangement
channels above 23 MeV.Comment: 8 pages, 6 figures, submitted to Phys. Rev.
Three-cluster breakup in deuteron-deuteron collisions: single-scattering approximation
We present results for the three-cluster breakup in deuteron-deuteron
collisions at 130 and 270 MeV deuteron beam energy. The breakup amplitude is
calculated using the first term in the Neumann series expansion of the
corresponding exact four-nucleon equations. In analogy with nucleon-deuteron
breakup where an equivalent approximation is compared with exact calculations,
we expect this single-scattering approximation to provide a rough estimation of
three-body breakup observables in quasifree configurations. We predict the
nucleon-deuteron and deuteron-deuteron three-cluster breakup cross sections to
be of a comparable size and thereby question the reliability of the recent
experimental data [A. Ramazani-Moghaddam-Arani, Ph.D. thesis, University of
Groningen, 2009; A. Ramazani-Moghaddam-Arani et al., EPJ Web of Conferences 3,
04012 (2010)] that is smaller by about three orders of magnitude. We also show
that an equivalent single-scattering approximation provides a reasonable
description of deuteron-deuteron elastic scattering at forward scattering
angles.Comment: 8 pages, 9 figures, submitted to Phys. Rev.
H production via neutron-neutron-deuteron recombination
We study the recombination of two neutrons and deuteron into neutron and
H using realistic nucleon-nucleon potential models. Exact Alt,
Grassberger, and Sandhas equations for the four-nucleon transition operators
are solved in the momentum-space framework using the complex-energy method with
special integration weights. We find that at astrophysical or laboratory
neutron densities the production of H via the neutron-neutron-deuteron
recombination is much slower as compared to the radiative neutron-deuteron
capture. We also calculate neutron-H elastic and total cross sections.Comment: accepted for publication in Phys. Rev.
Calculation of proton-He elastic scattering between 7 and 35 MeV
Background: Theoretical calculations of the four-particle scattering above
the four-cluster breakup threshold are technically very difficult due to
nontrivial singularities or boundary conditions. Further complications arise
when the long-range Coulomb force is present.
Purpose: We aim at calculating proton-He elastic scattering observables
above three- and four-cluster breakup threshold.
Methods: We employ Alt, Grassberger, and Sandhas (AGS) equations for the
four-nucleon transition operators and solve them in the momentum-space
framework using the complex-energy method whose accuracy and practical
applicability is improved by a special integration method.
Results: Using realistic nuclear interaction models we obtain fully converged
results for the proton-He elastic scattering. The differential cross
section, proton and He analyzing powers, spin correlation and spin
transfer coefficients are calculated at proton energies ranging from 7 to 35
MeV. Effective three- and four-nucleon forces are included via the explicit
excitation of a nucleon to a isobar.
Conclusions: Realistic proton-He scattering calculations above the
four-nucleon breakup threshold are feasible. There is quite good agreement
between the theoretical predictions and experimental data for the
proton-He scattering in the considered energy regime. The most remarkable
disagreements are the peak of the proton analyzing power at lower energies and
the minimum of the differential cross section at higher energies. Inclusion of
the isobar reduces the latter discrepancy.Comment: Submitted to Phys. Rev.
Four-body calculation of proton-3He scattering
The four-body equations of Alt, Grassberger and Sandhas are solved, for the
first time, for proton- scattering including the Coulomb
interaction between the three protons using the method of screening and
renormalization as it was done recently for proton-deuteron scattering. Various
realistic two-nucleon potentials are used. Large Coulomb effects are seen on
all observables. Comparison with data at different energies shows large
deviations in the proton analyzing power but quite reasonable agreement in
other observables. The effect of nucleon-nucleon magnetic moment interaction
and correlations between \pd and \pHe analyzing powers are studied.Comment: to be published in Phys. Rev. Let
Calculation of multichannel reactions in the four-nucleon system above breakup threshold
Exact four-body equations of Alt, Grassberger and Sandhas are solved for
neutron- and proton- scattering in the energy
regime above the four-nucleon breakup threshold. Cross sections and spin
observables for elastic, transfer, charge-exchange, and breakup reactions are
calculated using realistic nucleon-nucleon interaction models, including the
one with effective many-nucleon forces due to explicit -isobar
excitation. The experimental data are described reasonably well with only few
exceptions such as vector analyzing powers.Comment: 5 pages, 6 figures, to be published in Phys. Rev. Let
Faddeev equation approach for three-cluster nuclear reactions
In this lecture we aim to present a formalism based on Faddeev-like equations
for describing nuclear three-cluster reactions that include elastic, transfer
and breakup channels. Two different techniques based on momentum-space and
configuration-space representations are explained in detail. An important new
feature of these methods is the possibility to account for the repulsive
Coulomb interaction between two of the three clusters in all channels.
Comparison with previous calculations based on approximate methods used in
nuclear reaction theory is also discussed.Comment: Submitted to "Clusters in Nuclei Vol. 3
Treatment of the Coulomb interaction in three-nucleon reactions
The Coulomb interaction between the two protons is included in the
calculation of three-nucleon hadronic and electromagnetic reactions using
screening and renormalization approach. Calculations are done using integral
equations in momentum space. The reliability of the method is demonstrated. The
Coulomb effect on observables is discussed.Comment: Talk given at the 18th International IUPAP Conference on Few-Body
Problems in Physics, Santos, August 21 - 26, 200
- …