598 research outputs found
Non-adiabatic corrections to elastic scattering of halo nuclei
We derive the formalism for the leading order corrections to the adiabatic
approximation to the scattering of composite projectiles. Assuming a two-body
projectile of core plus loosely-bound valence particle and a model (the core
recoil model) in which the interaction of the valence particle and the target
can be neglected, we derive the non-adiabatic correction terms both exactly,
using a partial wave analysis, and using the eikonal approximation. Along with
the expected energy dependence of the corrections, there is also a strong
dependence on the valence-to-core mass ratio and on the strength of the
imaginary potential for the core-target interaction, which relates to
absorption of the core in its scattering by the target. The strength and
diffuseness of the core-target potential also determine the size of the
corrections. The first order non-adiabatic corrections were found to be smaller
than qualitative estimates would expect. The large absorption associated with
the core-target interaction in such halo nuclei as Be11 kills off most of the
non-adiabatic corrections. We give an improved estimate for the range of
validity of the adiabatic approximation when the valence-target interaction is
neglected, which includes the effect of core absorption. Some consideration was
given to the validity of the eikonal approximation in our calculations.Comment: 14 pages with 10 figures, REVTeX4, AMS-LaTeX v2.13, submitted to
Phys. Rev.
Effects of an induced three-body force in the incident channel of (d,p) reactions
A widely accepted practice for treating deuteron breakup in
reactions relies on solving a three-body Schr\"odinger equation with
pairwise -, - and - interactions. However, it was shown in
[Phys. Rev. C \textbf{89}, 024605 (2014)] that projection of the many-body
wave function into the three-body channel results in a
complicated three-body operator that cannot be reduced to a sum of pairwise
potentials. It contains explicit contributions from terms that include
interactions between the neutron and proton via excitation of the target .
Such terms are normally neglected. We estimate the first order contribution of
these induced three-body terms and show that applying the adiabatic
approximation to solving the model results in a simple modification of
the two-body nucleon optical potentials. We illustrate the role of these terms
for the case of Ca()Ca transfer reactions at incident
deuteron energies of 11.8, 20 and 56 MeV, using several parameterisations of
nonlocal optical potentials.Comment: 7 pages, 2 figures. Publication due in Phys. Rev.
Monte Carlo integration in Glauber model analysis of reactions of halo nuclei
Reaction and elastic differential cross sections are calculated for light
nuclei in the framework of the Glauber theory. The optical phase-shift function
is evaluated by Monte Carlo integration. This enables us to use the most
accurate wave functions and calculate the phase-shift functions without
approximation. Examples of proton nucleus (e.g. p-He, p-Li) and
nucleus-nucleus (e.g. HeC) scatterings illustrate the effectiveness
of the method. This approach gives us a possibility of a more stringent
analysis of the high-energy reactions of halo nuclei.Comment: 20 pages, 8 figure
Probing halo nucleus structure through intermediate energy elastic scattering
This work addresses the question of precisely what features of few body
models of halo nuclei are probed by elastic scattering on protons at high
centre-of-mass energies. Our treatment is based on a multiple scattering
expansion of the proton-projectile transition amplitude in a form which is well
adapted to the weakly bound cluster picture of halo nuclei. In the specific
case of Li scattering from protons at 800 MeV/u we show that because
core recoil effects are significant, scattering crosssections can not, in
general, be deduced from knowledge of the total matter density alone.
We advocate that the optical potential concept for the scattering of halo
nuclei on protons should be avoided and that the multiple scattering series for
the full transition amplitude should be used instead.Comment: 8 pages REVTeX, 1 eps figure, accepted for publication in Phys. Rev.
Energy Dependence of Breakup Cross Sections of Halo Nucleus 8B and Effective Interactions
We study the energy dependence of the cross sections for nucleon removal of
8B projectiles. It is shown that the Glauber model calculations with
nucleon-nucleon t-matrix reproduce well the energy dependence of the breakup
cross sections of 8B. A DWBA model for the breakup cross section is also
proposed and results are compared with those of the Glauber model. We show that
to obtain an agreement between the DWBA calculations, the Glauber formalism,
and the experimental data, it is necessary to modify the energy behavior of the
effective interaction. In particular, the breakup potential has a quite
different energy dependence than the strong absorption potential.Comment: 13 pages, 4 figure
Aldosterone modulates the association between NCC and ENAC
Distal sodium transport is a final step in the regulation of blood pressure. As such, understanding how the two main sodium transport proteins, the thiazide-sensitive sodium chloride cotransporter (NCC) and the epithelial sodium channel (ENaC), are regulated is paramount. Both are expressed in the late distal nephron; however, no evidence has suggested that these two sodium transport proteins interact. Recently, we established that these two sodium transport proteins functionally interact in the second part of the distal nephron (DCT2). Given their co-localization within the DCT2, we hypothesized that NCC and ENaC interactions might be modulated by aldosterone (Aldo). Aldo treatment increased NCC and αENaC colocalization (electron microscopy) and interaction (coimmunoprecipitation). Finally, with co-expression of the Aldo-induced protein serum- and glucocorticoid-inducible kinase 1 (SGK1), NCC and αENaC interactions were increased. These data demonstrate that Aldo promotes increased interaction of NCC and ENaC, within the DCT2 revealing a novel method of regulation for distal sodium reabsorption
Few-body multiple scattering calculations for 6 He on protons
The elastic scattering of the halo nucleus 6 He from a proton target at 717 MeV/nucleon is investigated within three different multiple-scattering formulations of the total transition amplitude. The factorized impulse
approximation (FIA) and the fixed scatterer approximation (FSA) of the multiple-scattering expansion are used to evaluate accurately the single-scattering terms and to test the validity of a few-body Glauber approach. The latter also includes terms beyond single scattering and the importance of these terms is investigated. The differential cross section is calculated for proton scattering from 6 He at 717 MeV in inverse kinematics and compared with recent data.Fundacao para a Ciencia e a Tecnologia POCTI/FNU/43421/2001Acçao Integrada Luso-Espanhola E-75/0
Probing the Structure of Halo Nuclei
Our understanding of halo nuclei has so far relied on high-energy scattering
and reactions, but a number of uncertainties remain. I discuss in general terms
the new range of observables which will be measured by experiments around the
Coulomb barrier, and how some details of the reaction mechanisms still need to
be clarified.Comment: Proceedings of FUSION97 conference (March 1997), South Durras,
Australia. Submitted to J. Physics G: special issue `Heavy ion collisions at
near barrier energies'. No figures; uses IOPConf.sty (included
Alternative evaluations of halos in nuclei
Data for the scattering of 6He, 8He, 9Li, and 11Li from hydrogen are analyzed
within a fully microscopic folding model of proton-nucleus scattering. Current
data suggest that of these only 11Li has a noticeable halo. For 6He, we have
also analysed the complementary reaction 6Li(gamma,pi)6He(gs). The available
data for that reaction support the hypothesis that 6He may not be a halo
nucleus. However, those data are scarce and there is clearly a need for more to
elicit the microscopic structure of 6He.Comment: 18 pages, 8 figures (added 4 figures), added reference. Version
accepted for publication in Phys. Rev.
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