1,656 research outputs found
Scaling and isospin effects in quasielastic lepton-nucleus scattering in the Relativistic Mean Field Approach
The role of isospin in quasielastic electron scattering and charge-changing
neutrino reactions is investigated in the relativistic impulse approximation.
We analyze proton and neutron scaling functions making use of various
theoretical descriptions for the final-state interactions, focusing on the
effects introduced by the presence of strong scalar and vector terms in the
relativistic mean field approach. An explanation for the differences observed
in the scaling functions evaluated from and reactions is
provided by invoking the differences in isoscalar and isovector contributions.Comment: 10 pages, 5 figures, submitted to Phys. Lett.
An optimized thermal extraction system for preparation of water from fluid inclusions in speleothems.
The fluid inclusions present in speleothems (secondary mineral deposits formed in caves) are a relict sample of the parent seepage water from which the speleothem was deposited and determination of their composition can solve the palaeotemperature equation for the precipitation of speleothem carbonate. We have extracted fluid inclusions using a newly-designed thermal vacuum extraction method in stalagmites and stalactites from Nerja Cave, Southern Spain. Optimal conditions were found to involve heating samples crushed to 0.8-2mm for 3 hours at 300-400ºC. Waters extracted from modern aragonitic speleothem samples produced results on the Meteoric Water Line defined by modern infiltration and other waters associated with the cave and hence demonstrate an absence of fractionation effects. This successfully demonstrates the utility of the method
Superscaling and Charge-changing Neutrino Cross Sections
The superscaling function extracted from inclusive electron scattering data
is used to predict high energy charge-changing neutrino cross sections in the
quasi-elastic and regions.Comment: 3 pages, 2 figures, to appear in the Proceedings of the 7th
International Workshop on Neutrino Factories and Superbeams, Laboratori
Nazionali di Frascati, Frascati (Rome), June 21 - 26, 200
Skewed recoil polarization in (e,e'p) reactions from polarized nuclei
The general formalism describing reactions,
involving polarization of the electron beam, target and ejected proton, is
presented within the framework of the relativistic plane wave impulse
approximation for medium and heavy nuclei. It is shown that the simultaneous
measurement of the target and ejected proton polarization can provide new
information which is not contained in the separate analysis of the
and reactions. The polarization
transfer mechanism in which the electron interacts with the initial nucleon
carrying the target polarization, making the proton exit with a fractional
polarization in a different direction, is referred to here as ``skewed
polarization''. The new observables characterizing the process are identified,
and written in terms of polarized response functions and asymmetries which are
of tensor nature. The corresponding half-off-shell single-nucleon responses are
analyzed using different prescriptions for the electromagnetic vertex and for
different kinematics. Numerical predictions are presented for selected
perpendicular and parallel kinematics in the case of K as polarized
target.Comment: 30 pages, 8 figure
Final state interaction effects in neutrino-nucleus quasielastic scattering
We consider the charged-current quasielastic scattering of muon neutrinos on
an Oxygen 16 target, described within a relativistic shell model and, for
comparison, the relativistic Fermi gas. Final state interactions are described
in the distorted wave impulse approximation, using both a relativistic mean
field potential and a relativistic optical potential, with and without
imaginary part. We present results for inclusive cross sections at fixed
neutrino energies in the range 200 MeV - 1 GeV, showing that final
state interaction effects can remain sizable even at large energies.Comment: 4 pages, 4 figures; poster session of the Third International
Workshop on Neutrino-Nucleus Interactions in the Few GeV Region (NuInt04),
Gran Sasso (Italy), March 17-21, 2004; to appear in the proceeding
Inclusive quasielastic scattering of polarized electrons from polarized nuclei
The inclusive quasielastic response functions that appear in the scattering
of polarized electrons from polarized nuclei are computed and analyzed for
several closed-shell-minus-one nuclei with special attention paid to 39K.
Results are presented using two models for the ejected nucleon --- when
described by a distorted wave in the continuum shell model or by a plane wave
in PWIA with on- and off-shell nucleons. Relativistic effects in kinematics and
in the electromagnetic current have been incorporated throughout. Specifically,
the recently obtained expansion of the electromagnetic current in powers only
of the struck nucleon's momentum is employed for the on-shell current and the
effects of the first-order terms (spin-orbit and convection) are compared with
the zeroth-order (charge and magnetization) contributions. The use of polarized
inclusive quasielastic electron scattering as a tool for determining
near-valence nucleon momentum distributions is discussed.Comment: 51 LaTeX pages, 14 Postscript figure
Superscaling analysis of the Coulomb Sum Rule in quasielastic electron-nucleus scattering
The Coulomb sum rule for inclusive quasielastic electron scattering in
C, Ca and Fe is analyzed based on scaling and superscaling
properties. Results obtained in the relativistic impulse approximation with
various descriptions of the final state interactions are shown. A comparison
with experimental data measured at Bates and Saclay is provided. The
theoretical description based on strong scalar and vector terms present in the
relativistic mean field, which has been shown to reproduce the experimental
asymmetric superscaling function, leads to results that are in fair agreement
with Bates data while it sizeably overestimates Saclay data. We find that the
Coulomb sum rule for a momentum transfer saturates to a
value close to 0.9, being very similar for the three nuclear systems
considered. This is in accordance with Bates data, which indicates that these
show no significative quenching in the longitudinal response.Comment: 22 pages, 6 figures. To be published in Phys. Lett.
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