14,430 research outputs found
Sensitivity of 8B breakup cross section to projectile structure in CDCC calculations
Given the Astrophysical interest of BeB, there have been
several experiments applying the Coulomb dissociation method for extracting the
capture rate. Measurements at Michigan State are dominated by
contributions but have a small component. On the other hand, a lower
energy measurement at Notre Dame has a much stronger contribution. The
expectation was that the two measurements would tie down the and thus
allow for an accurate extraction of the relevant for the capture process.
The aim of this brief report is to show that the factor in breakup
reactions does not translate into a scaling of the contribution in the
corresponding capture reaction. We show that changes to the B single
particle parameters, which are directly related to the component in the
capture reaction, do not effect the corresponding breakup reactions, using the
present reaction theory.Comment: 4 pages, 6 figures, revtex
Extracting (n,g) direct capture cross sections from Coulomb dissociation: application to C(n,)C
A methodology for extracting neutron direct capture rates from Coulomb
dissociation data is developed and applied to the Coulomb dissociation of 15C
on 208Pb at 68 MeV/nucleon. Full Continuum Discretized Coupled Channel
calculations are performed and an asymptotic normalization coefficient is
determined from a fit to the breakup data. Direct neutron capture calculations
using the extracted asymptotic normalization coefficient provide
cross sections consistent with direct measurements. Our results show that the
Coulomb Dissociation data can be reliably used for extracting the cross section
for 14C(n,g)15C if the appropriate reaction theory is used. The resulting error
bars are of comparable magnitude to those from the direct measurement. This
procedure can be used more generally to extract capture cross sections from
breakup reactions whenever the desired capture process is fully peripheral.Comment: submitted to Phys. Rev. C (R
Understanding low energy reaction with exotic nuclei
Recent developments on the understanding of low energy reactions are
highlighted. Emphasis is given to the CDCC framework where the breakup channels
of the projectile are included explicitly. Properties of the breakup couplings
are presented. Comments are given with regard to the separation between the
nuclear and the Coulomb contributions to breakup cross sections as well as the
dependence on the optical potentials. A discussion on the sensitivity of the
CDCC basis is discussed, by comparing pure breakup results with transfer to the
continuum calculations. Finally, some remaining controversies show the need to
go beyond the single particle picture for the projectile.Comment: Proceedings from 'Nuclei at the limits', ANL 26-30 July 2004, 6 pages
and 8 figure
Beach and cliff retreat induced by storm groups at Forte Novo,Algarve (Portugal)
Littoral cell dynamics may change through time as a reaction to modifications of the coastal system. Along the Vilamoura-Quarteira coastline, the construction of a groin field limited the sediment supply to the already narrow Forte Novo beach, located downdrift, enhanced wave action on the cliff base and lead to long-term persistent cliff retreat. This research uses a set of surveys from November 2009 to March 2010 to determine short-term soft cliff erosion associated to storm groups at this sediment starved area. Following the initial LiDAR survey, three subsequent surveys were performed using a reflectorless total station for monitoring the cliff face, and RTK-DGPS to monitor the position of the cliff top, the cliff foot and the topography of the adjacent beach. Results indicate an important reduction in beach levels during successive storms (without significant beach recovery in between), allowing waves to further attack the cliff base and contributing to further enhance the structural and permanent cliff retreat. This work demonstrates how a combination of magnitude and frequency of extreme events coupled with development of the coastline, has led to increased cliff-beach recession and to the permanent dislocation of the cliff face
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