Validity of the distorted-wave impulse-approximation description of Ca40(e,e′p)K39

Abstract

The nonlocal implementation of the dispersive optical model (DOM) provides all the ingredients for distorted-wave impulse-approximation (DWIA) calculations of the (e, e ′ p) reaction. It provides both the overlap function, including its normalization, and the outgoing proton distorted wave. This framework is applied to describe the knockout of a proton from the 0d 3 2 and 1s 1 2 orbitals in 40 Ca with fixed normalizations of 0.71 and 0.60, respectively. Data were obtained in parallel kinematics for three outgoing proton energies: 70, 100, and 135 MeV. Agreement with the data is as good as, or better than, previous descriptions employing local optical potentials and overlap functions from Woods-Saxon potentials -both with standard nonlocality corrections -whose normalization (spectroscopic factor) and radius were fitted to the data. The present analysis suggests that slightly larger spectroscopic factors are obtained when nonlocal optical potentials are employed than those generated with local potentials. The results further suggest that the chosen kinematical window around 100 MeV proton energy provides the best and cleanest method to employ the DWIA for the analysis of this reaction. The conclusion that substantial ground-state correlations cannot be ignored when describing a closed-shell atomic nucleus is therefore confirmed in detail. To reach these conclusions, it is essential to have a complete description of the nucleon single-particle propagator that accounts for all elastic nucleon-scattering observables in a wide energy domain up to 200 MeV. The current nonlocal implementation of the DOM fulfills this requirement.

Dispersive optical model analysis of Pb208 generating a neutron-skin prediction beyond the mean field

“…While the use of nonlocal optical potentials may slightly increase this value as shown in Ref. [17], it may be concluded that the value of 0.69 obtained from the present analysis is completely consistent with this result. Nikhef data obtained in a large missing energy and momentum domain [54] can therefore now be consistently analyzed employing the complete DOM spectral functions.…”

“…This factor can be probed using the exclusive (e, e p) reaction as discussed in Ref. [17]. Note that because of the presence of imaginary parts of the self-energy at other energies, there is also strength located there, thus the spectroscopic factor will be less than 1 and also less than the occupation probability.…”

“…Implementations of the nonlocal DOM in 40 Ca and 48 Ca have previously been published in Refs. [15,17,23].…”

Investigating the link between proton reaction cross sections and the quenching of proton spectroscopic factors in 48Ca

“…In Ref. [9], a nonlocal dispersive optical model (DOM) which simultaneously describes both bound and scattering states was used to consistently provide all ingredients, including spectroscopic factors, for an accurate DWIA description of 40 Ca(e, e p) 39 K data.…”

“…To investigate this discrepancy, a consistent DWIA analysis of 48 Ca(e, e p) 47 K is performed using a nonlocal DOM description similar to the one reported in Ref. [9] for 40 Ca. Comparing the DOM calculated spectroscopic factors of 48 Ca and 40 Ca will provide more information on the quenching of proton spectroscopic factors when neutrons are added.…”