Speaker
Carlos Bertulani
(Department of Physics, University of Arizona, Tucson, AZ)
Description
Precise nuclear reaction rates are needed for a detailed description of the
production of elements in primordial nucleosynthesis and during the
hydrostatic burning of stars to constrain the astrophysical models. The
relevant reactions are extremely difficult to measure directly in the
laboratory at the small astrophysical energies [1]. In recent years several
indirect methods have been developed and applied to extract low-energy
astrophysical S factors. Here, the methods of Coulomb dissociation, of the
asymptotic normalization coefficient (ANC) and the Trojan-Horse method will be
discussed. The application of these indirect methods requires a combination of
experimental and theoretical efforts. This contribution focuses on the
underlying reaction theories that have to be understood well in order to
assess the precision and limitations of the various approaches [2].
Studying nuclear structure and nuclear reactions within a consistent approach
is a complicated issue in nuclear physics. Here I will report on an attempt to
reconcile structure and reactions in the No-Core Shell-Model (NCSM). The
principal foundation of the NCSM is the use of effective interactions
appropriate for the large, but finite, basis spaces employed in the
calculations. These effective interactions are derived from the underlying
realistic inter-nucleon potentials by a unitary transformation in a way that
guarantees convergence to the exact solution as the basis size increases. It
is a challenging task to extend ab initio nuclear structure approaches to the
description of nuclear reactions. I will present the first calculations of the
$^{7}$Be(p,$\gamma$)$^{8}$B S-factor starting from the ab initio NCSM wave
functions of $^{7}$Be and $^{8}$B bound states [3]. These wave functions were
obtained in basis spaces up to 10$\hbar\omega$ and used to calculate channel
cluster form factors (overlap integrals) of the $^{8}$B ground state with
$^{7}$Be+p. Due to the use of the harmonic oscillator (HO) basis, the overlap
integrals have incorrect asymptotic properties. We fix this problem in two
alternative ways. First, by a Woods-Saxon potential solution fit to the
interior of the NCSM overlap integrals. Second, by a direct matching with the
Whittaker function. The corrected overlap integrals are then used for the
$^{7}$Be(p,$\gamma$)$^{8}$B S-factor calculation.
\vspace{12pt}
\parindent=0pt \textbf{References}
[1] C.A. Bertulani, Phys. Lett. B 585 (2004) 35
[2] C.A.Bertulani, Phys. Rev. Lett. 94, 072701 (2005)
[3] P. Navratil, C.A. Bertulani, and E. Caurier, Phys. Lett. B 634 (2006) 191;
Phys. Rev. C, in press.
Author
Carlos Bertulani
(Department of Physics, University of Arizona, Tucson, AZ)