671 research outputs found
Test of Fermi Gas Model and Plane-Wave Impulse Approximation Against Electron-Nucleus Scattering Data
A widely used relativistic Fermi gas model and plane-wave impulse
approximation are tested against electron-nucleus scattering data. Inclusive
quasi-elastic cross section are calculated and compared with high-precision
data for C, O, and Ca. A dependence of agreement between calculated cross
section and data on a momentum transfer is shown. Results for the C(nu_mu,mu)
reaction are presented and compared with experimental data of the LSND
collaboration.Comment: 10 pages, 8 figure
Quasi-elastic neutrino charged-current scattering cross sections on oxygen
The charged-current quasi-elastic scattering of muon neutrinos on oxygen
target is computed for neutrino energies between 200 MeV and 2.5 GeV using the
relativistic distorted-wave impulse approximation with relativistic optical
potential, which was earlier successfully applied to describe electron-nucleus
data. We study both neutrino and electron processes and show that the reduced
exclusive cross sections for neutrino and electron scattering are similar. The
comparison with the relativistic Fermi gas model (RFGM), which is widely used
in data analyses of neutrino experiments, shows that the RFGM fails completely
when applied to exclusive cross section data and leads to overestimated values
of inclusive and total cross sections. We also found significant nuclear-model
dependence of exclusive, inclusive and total cross sections for about 1 GeV
energy.Comment: 30 pages, 11 figures; final version to appear in Phys. Rev.
Analysis of quasi-elastic neutrino charged-current scattering off O and neutrino energy reconstruction
The charged-current quasi-elastic scattering of muon neutrino on the oxygen
target is analyzed for neutrino energy up to 2.5 GeV using the Relativistic
Distorted-Wave Impulse Approximation (RDWIA). The inclusive cross sections
, calculated within the RDWIA, are lower than the Relativistic
Fermi Gas Model (RFGM) results in the range of the square of four-momentum
transfer 0.2 (GeV/c). We have also studied the nuclear-model
dependence of the neutrino energy reconstruction accuracy using the
charged-current quasi-elastic events with no detector effects and background.
We found that for one-track events the accuracy is nuclear-model dependent for
neutrino energy up to 2.5 GeV.Comment: 29 pages, 10 figure
Exclusive production in proton-nucleus collisions
The exclusive meson production in a proton-nucleus collision, leading
to two body final states, is investigated in a fully covariant two-nucleon
model based on the effective Lagrangian picture. The explicit kaon production
vertex is described via creation, propagation and decay into relevant channel
of (1650), (1710) and (1720) intermediate baryonic states in the
initial collision of the projectile nucleon with one of its target counterparts
which is modeled by the one-pion exchange process. The calculated cross
sections show strong sensitivity to the medium effects on pion propagator and
to the final hypernuclear state excited in the reaction.Comment: Two new figures, version accepted for publication by Phys. Rev.
Rescaling of Nuclear Structure Functions
It is shown that nucleonic structure functions are and rescaled
in nuclei. The rescaling accounts for nuclear effects in the case of exact
scaling, while the rescaling is responsible for a corresponding
modification of quantum corrections. This result is obtained in the leading
order for all flavour combinations and connects the two known models for the
EMC-effect. Electroproduction and gluonic nuclear structure functions are
calculated.Comment: 9 pages, Latex, 2 figures appended (compressed and uuencoded
Induced Nucleon Polarization and Meson-Exchange Currents in (e,e'p) Reactions
Nucleon recoil polarization observables in reactions are
investigated using a semi-relativistic distorted-wave model which includes one-
and two-body currents with relativistic corrections. Results for the induced
polarization asymmetry are shown for closed-shell nuclei and a comparison with
available experimental data for C is provided. A careful analysis of
meson exchange currents shows that they may affect significantly the induced
polarization for high missing momentum.Comment: 7 pages, 9 figures. Revised version with small changes, new curve in
Fig. 3. To be published in PR
Kinetic energy sum spectra in nonmesonic weak decay of hypernuclei
We evaluate the coincidence spectra in the nonmesonic weak decay (NMWD)
\Lambda N\go nN of hypernuclei He, He,
C, O, and Si, as a function of the
sum of kinetic energies for . The strangeness-changing
transition potential is described by the one-meson-exchange model, with
commonly used parameterization. Two versions of the Independent-Particle Shell
Model (IPSM) are employed to account for the nuclear structure of the final
residual nuclei. They are: (a) IPSM-a, where no correlation, except for the
Pauli principle, is taken into account, and (b) IPSM-b, where the highly
excited hole states are considered to be quasi-stationary and are described by
Breit-Wigner distributions, whose widths are estimated from the experimental
data. All and spectra exhibit a series of peaks in the energy
interval 110 MeV MeV, one for each occupied shell-model state.
The IPSM-a could be a pretty fair approximation for the light He
and He hypernuclei. For the remaining, heavier, hypernuclei it is
very important, however, to take into account the spreading in strength of the
deep-hole states, and bring into play the IPSM-b approach. Notwithstanding the
nuclear model that is employed the results depend only very weakly on the
details of the dynamics involved in the decay process proper. We propose that
the IPSM is the appropriate lowest-order approximation for the theoretical
calculations of the of kinetic energy sum spectra in the NMWD. It is in
comparison to this picture that one should appraise the effects of the final
state interactions and of the two-nucleon-induced decay mode.Comment: v1: 20 pages, 3 figures, 1 table, submitted for publication; v2:
minor corrections, improved figures, published versio
Correlations in Nuclei: Self-Consistent Treatment and the BAGEL Approach
An approach is presented which allows a self-consistent description of the
fragmentation of single-particle strength for nucleons in finite nuclei
employing the Greens function formalism. The self-energy to be considered in
the Dyson equation for the single-particle Greens function contains all terms
of first (Hartree-Fock) and second order in the residual interaction. It is
demonstrated that the fragmentation of the single-particle strength originating
from the terms of second order can efficiently be described in terms of the
so-called BAGEL approximation. Employing this approximation the self-energy can
be evaluated in a self-consistent way, i.e. the correlations contained in the
Greens function are taken into account for the evaluation of the self-energy.
As an example this scheme is applied to the nucleus , using a realistic
nucleon nucleon interaction. The effects of the correlations on the occupation
probabilities and the binding energy are evaluated.Comment: 9 page
Final-State Interactions in (e,e'p) Reactions with Polarized Nuclei
The cross section for coincidence, quasielastic proton knock-out by electrons
from a polarized K39 nucleus is computed in DWIA using an optical potential in
describing the wave function of the ejected nucleon. The dependence of the FSI
on the initial polarization angles of the nucleus is analyzed and explained in
a new, semi-classical picture of the reaction in which the nuclear transparency
decreases as a function of the amount of nuclear matter that the proton has to
cross, thus providing a method for obtaining detailed information on its mean
free path in finite nuclei. We propose a procedure to find the best initial
kinematical conditions for minimizing the FSI which will be useful as a guide
for future experiments with polarized nuclei.Comment: 26 pages, 8 Postscript figures, uses epsf.st
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