nucl-th digest · Dec 17, 2020

Recent advances in the quantification of uncertainties in reaction theory

Uncertainty quantification has become increasingly more prominent in nuclear physics over the past several years. In few-body reaction theory, there are four main sources that contribute to the uncertainties in the calculated observables: the effective potentials, approximations made to the few-body problem, structure functions, and degrees of freedom left out of the model space. In this work, we illustrate some of the features that can be obtained when modern statistical tools are applied in the context of nuclear reactions. This work consists of a summary of the progress that has been made in quantifying theoretical uncertainties in this domain, focusing primarily on those uncertainties coming from the effective optical potential as well as their propagation within various reaction theories. We use, as the central example, reactions on the doubly-magic stable nucleus

^{40}

Ca, namely neutron and proton elastic scattering and single-nucleon transfer

^{40}

Ca(d,p)

^{41}

Ca. First, we show different optimization schemes used to constrain the optical potential from differential cross sections and other experimental constraints; we then discuss how these uncertainties propagate to the transfer cross section, comparing two reaction theories. We finish by laying out our future plans.

Comments:: 28 pages, 7 figures, J Phys. G
Subjects:: Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:: 2012.09012 [pdf]

J.Phys.G(2020)·34 citations

[Submitted on 8 Dec 2020]

Determination of matter radius and neutron skin of $^{58}$ Ni from reaction cross section of proton+ $^{58}$ Ni scattering based on chiral $g$ -matrix model

Shingo Tagami · Maya Takechi · Jun Matsui · Tomotsugu Wakasa · Masanobu Yahiro

Background: Using the chiral (Kyushu) $g$ -matrix folding model with the densities calculated with Gogny-HFB (GHFB) with the angular momentum projection (AMP), we determined the central values of matter radius and neutron skin from the central values of reaction cross sections $σ_{R} (EXP)$ of p+ $^{40, 48}$ Ca and p+ $^{208}$ Pb scattering. As for p+ $^{58}$ Ni scattering, $σ_{R} (EXP)$ are available as a function of incident energy $E_{in}$ . Aim: Our aim is to determine matter radius $r_{m}$ and skin $r_{skin}$ for $^{58}$ Ni from the $σ_{R} (EXP)$ of p+ $^{58}$ Ni scattering by using the Kyushu $g$ -matrix folding model with the GHFB+AMP densities. Results: For p+ $^{58}$ Ni scattering, the Kyushu $g$ -matrix folding model with the GHFB+AMP densities reproduces $σ_{R} (EXP)$ in $8.8 \leq E_{in} \leq 81$ MeV. For $E_{in} = 81$ MeV, we define the factor $F$ as $F = σ_{R} (EXP) / σ_{R} (AMP) = 0.9775$ . The $F σ_{R} (AMP)$ be much the same as the center values of $σ_{R} (EXP)$ in $8.8 \leq E_{in} \leq 81$ MeV. We then determine $r_{m} (EXP)$ from the center values of $σ_{R} (EXP)$ , using $σ_{R} (EXP) = C r_{m}^{2} (EXP)$ with $C = r_{m}^{2} (AMP) / (F σ_{R} (AMP))$ . The $r_{m} (EXP)$ thus obtained are averaged over $E_{in}$ . The averaged value is $r_{m} (EXP) = 3.697$ fm. Eventually, we obtain $r_{skin} (EXP) = 0.023$ fm from $r_{m} = 3.697$ fm and $r_{p} (EXP) = 3.685$ fm of electron scattering.

Comments:: arXiv admin note: substantial text overlap with arXiv:2011.12235, arXiv:2012.01063
Subjects:: Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:: 2012.09146 [pdf]

0 citations

Thursday·December 17, 2020

Recent advances in the quantification of uncertainties in reaction theory

Determination of matter radius and neutron skin of $^{58}$ Ni from reaction cross section of proton+ $^{58}$ Ni scattering based on chiral $g$ -matrix model

Affiliations

Recent advances in the quantification of uncertainties in reaction theory

Determination of matter radius and neutron skin of 58Ni from reaction cross section of proton+58Ni scattering based on chiral g-matrix model

Affiliations

Determination of matter radius and neutron skin of $^{58}$ Ni from reaction cross section of proton+ $^{58}$ Ni scattering based on chiral $g$ -matrix model