Optical model analysis of quasielastic (p, n) reactions at 22.8 Mev

Symmetry energy III: Isovector skins

“…In our work, we find both to be of importance when deciding on the subtle details of the Lane potential, even though the contributions of the isovector potential to the nucleonic potentials are nominally small, ∼ |N − Z|/A. Both Jon et al [18,31] and Carlson et al [27,28] were able to assign values of radii and surface diffuseness to isovector potentials on a nucleus-by-nucleus basis and these turned out to vary relatively smoothly with nuclear mass. Even though we work with larger data sets with smaller errors for individual nuclei, we find those data insufficient to constrain reliably such an abundance of parameters for isovector potentials, on a meaningful scale, as in the works above.…”

“…When the proton and neutron potentials have significant differences in their geometry, though, such as in the "best-fit" case of the BG parametrization [29], the resulting isovector potential can have unusual structure [43] difficult to justify on physical grounds. Carlson et al [28] and Jon et al [18,31], in fact, postulated…”

“…On the other hand, Patterson et al [15] described a comprehensive set of (p,n) data from their measurements, in parallel with reference elastic (p,p) and (n,n) cross sections, using single geometry of the BG proton potential for both the isovector and the isoscalar potentials. Jon et al [18,31] adjusted geometry of the imaginary part of isovector potential to reproduce their cross-section measurements for (p,n) reactions at 35 MeV, while keeping the real part in the BG form, largely continuing the effort of Carlson et al [27,28].…”

Folding model study of the isobaric analog excitation: Isovector density dependence, Lane potential, and nuclear symmetry energy

“…Since the elastic neutron scattering on a target being in its excited IAS cannot be measured (most IAS's are either a short-lived bound state or an unbound resonance), we have determined U n from the isoscalar U 0 and isovector U 1 parts of the proton-nucleus OP evaluated at the effective incident energy E = E lab − Q/2, using Eq. (9). The existing nucleon-nucleus global OP's [6][7][8] have been carefully determined based on large experimental databases of both the elastic nucleon-nucleus scattering and analyzing power angular distributions, and it is natural to use them to construct U p for our study.…”

“…While these three global nucleon optical potentials have been widely used in predicting the nucleon-nucleus OP in numerous direct reaction analyses within the DWBA or coupled-channel (CC) formalism, their isospin dependence has been rarely used to study the charge exchange (p, n) transition between the IAS's. The (phenomenological) Lane potential U 1 has been studied in detail so far at some particular energies only, such as the systematics for U 1 deduced from IAS data of the (p, n) reaction measured at 22.8 [9] and 35 MeV [10]. Therefore, it is necessary to have a reliable microscopic prediction for U 1 by the folding model, to reduce the uncertainty associated with the isospin dependence of the nucleon-nucleus OP.…”