3,639 research outputs found
Superscaling and neutral current quasielastic neutrino-nucleus scattering
The superscaling approach is applied to studies of neutral current neutrino
reactions in the quasielastic regime. Using input from scaling analyses of
electron scattering data, predictions for high-energy neutrino and antineutrino
cross sections are given and compared with results obtained using the
relativistic Fermi gas model. The influence of strangeness content inside the
nucleons in the nucleus is also explored.Comment: 28 pages, 8 figures, accepted for publication in Phys.Rev.
Radiative pion capture in nuclei: a continuum shell-model approach
The radiative pion capture process in nuclei is approached by using a
continuum shell-model description of the nucleus, together with a
phenomenological treatment of the two particle-two hole effects. It is found
that these effects play an important role to reproduce the observed
experimental photon energy distribution. This distribution as well as the
integrated one depends significantly on the details of the mean field
potential. This makes this process interesting to investigate the nuclear
structure dynamics.Comment: 21 pages, LateX file + 5 figures, epsf.st
Analysis of Meson Exchange and Isobar Currents in (e,e'p) Reactions from O-16
An analysis of the effects of meson exchange and isobar currents in exclusive
(e,e'p) processes from O-16 under quasi-free kinematics is presented. A model
that has probed its feasibility for inclusive quasi-elastic (e,e') processes is
considered. Sensitivity to final state interactions between the outgoing proton
and the residual nucleus is discussed by comparing the results obtained with
phenomenological optical potentials and a continuum nuclear shell-model
calculation. The contribution of the meson-exchange and isobar currents to the
response functions is evaluated and compared to previous calculations, which
differ notably from our results. These two-body contributions cannot solve the
puzzle of the simultaneous description of the different responses
experimentally separated. Copyright 1999 by The American Physical SocietyComment: 5 pages, plus 3 PS figures. To be published in Phys. Rev. C Updated
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Equivalence between local Fermi gas and shell models in inclusive muon capture from nuclei
Motivated by recent studies of inclusive neutrino nucleus processes and muon
capture within a correlated local Fermi gas model (LFG), we discuss the
relevance of nuclear finite size effects in these reactions at low energy, in
particular for muon capture. To disentangle these effects from others coming
from the reaction dynamics we employ here a simple uncorrelated shell model
that embodies the typical finite size content of the problem. The integrated
decay widths of muon atoms calculated with this shell model are then compared
for several nuclei with those obtained within the uncorrelated LFG, using in
both models exactly the same theoretical ingredients and parameters. We find
that the two predictions are in quite good agreement, within 1--7%, when the
shell model density and the correct energy balance is used as input in the LFG
calculation. The present study indicates that, despite the low excitation
energies involved in the reaction, integrated inclusive observables, like the
total muon capture width, are quite independent of the fine details of the
nuclear wave functions.Comment: 11 pages, 8 figures. Final version to be published in EPJ
Local Fermi gas in inclusive muon capture from nuclei
We compare local Fermi gas and shell model in muon capture in nuclei in order
to estimate the effect of finite nuclear size in low energy weak reactions.Comment: 6 pages, 8 figures. To be published in the Proceedings of 20th Max
Born Symposium, Wroclaw (Poland), December 7-10, 200
Using Electron Scattering Superscaling to predict Charge-changing Neutrino Cross Sections in Nuclei
Superscaling analyses of few-GeV inclusive electron scattering from nuclei
are extended to include not only quasielastic processes, but now also into the
region where -excitation dominates. It is shown that, with reasonable
assumptions about the basic nuclear scaling function extracted from data and
information from other studies of the relative roles played by correlation and
MEC effects, the residual strength in the resonance region can be accounted for
through an extended scaling analysis. One observes scaling upon assuming that
the elementary cross section by which one divides the residual to obtain a new
scaling function is dominated by the transition and employing a
new scaling variable which is suited to the resonance region. This yields a
good representation of the electromagnetic response in both the quasielastic
and regions. The scaling approach is then inverted and predictions are
made for charge-changing neutrino reactions at energies of a few GeV, with
focus placed on nuclei which are relevant for neutrino oscillation
measurements. For this a relativistic treatment of the required weak
interaction vector and axial-vector currents for both quasielastic and
-excitation processes is presented.Comment: 42 pages, 9 figures, accepted for publication in Physical Review
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
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