Nuclear Theory·nucl-th

Monday·January 24, 2022

8 papers—3 primary·5 cross-listed

01
[Submitted on 21 Jan 2022]
Neutron skin in $^{48}$ Ca determined from p+ $^{48}$ Ca and $^{48}$ Ca+ $^{12}$ C scattering
Shingo Tagami · Tomotsugu Wakasa · Maya Takechi · Jun Matsui · Masanobu Yahiro
In our previous paper, we determined $r_{skin}^{208} (exp) = 0.278 \pm 0.035$ ~fm from $σ_{R}$ for p+ $^{208}$ Pb scattering, using the Kyushu (chiral) $g$ -matrix folding model with the densities calculated with D1S-GHFB with the angular momentum projection (AMP). The value agrees with that of PREX2. Reaction cross sections $σ_{R}$ are available for p+ $^{48}$ Ca scattering, whereas interaction cross sections $σ_{I}$ are available for $^{48}$ Ca + $^{12}$ C scattering. As for $^{48}$ Ca, the high-resolution $E 1$ polarizability experiment ( $E 1$ pE) yields $r_{skin}^{48} (E 1 pE) = 0.14 \sim 0.20 fm$ . We determine $r_{skin}^{48} (exp)$ from the data on $σ_{R}$ for p+ $^{48}$ Ca scattering and from the data on $σ_{I}$ for $^{48}$ Ca+ $^{12}$ C scattering. We use the Kyushu $g$ -matrix folding model with the densities calculated with the D1M-GHFB+AMP densities. The D1M-GHFB+AMP proton and neutron densities are scaled so as to reproduce the data under the condition that the radius $r_{p}$ of the scaled proton density equals the data $r_{p} (exp)$ determined from the electron scattering. We deduce skin values $r_{skin} = r_{n} (exp) - r_{p} (exp)$ from the resulting $r_{n} (exp)$ and the $r_{p} (exp)$ determined from electron scattering. The same procedure is taken for D1S-GHFB+AMP. We regard $r_{skin}^{48} (E 1 pE)$ as a reference skin value. Using the reference skin value and taking D1M-GHFB+AMP, we determine $r_{skin}^{48} (exp) = 0.158 \pm 0.025$ ~fm for p+ $^{48}$ Ca scattering and $0.160 \pm 0.058$ ~fm for $^{48}$ Ca + $^{12}$ C scattering. We take the weighted mean and its error for the two skin values. The result is $r_{skin}^{48} (exp) = 0.158 \pm (0.023)_{exp} \pm (0.012)_{th} fm$ .
Comments:
arXiv admin note: substantial text overlap with arXiv:2107.06441
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2201.08541 [pdf]
6 citations
02
[Submitted on 21 Jan 2022]
Controlling extrapolations of nuclear properties with feature selection
Rodrigo Navarro Perez · Nicolas Schunck
Predictions of nuclear properties far from measured data are inherently imprecise because of uncertainties in our knowledge of nuclear forces and in our treatment of quantum many-body effects in strongly-interacting systems. While the model bias can be directly calculated when experimental data is available, only an estimate can be made in the absence of such measurements. Current approaches to compute the estimated bias quickly lose predictive power when input variables such as proton or neutron number are extrapolated, resulting in uncontrolled uncertainties in applications such as nucleosynthesis simulations. In this letter, we present a novel technique to identify the input variables of machine learning algorithms that can provide robust estimates of model bias. Our process is based on selecting input variables, or features, based on their probability distribution functions across the entire nuclear chart. We illustrate our approach on the problem of quantifying the model bias in nuclear binding energies calculated with Density Functional Theory (DFT). We show that feature selection can systematically improve theoretical predictions without increasing uncertainties.
Comments:
Manuscript: 6 pages. Supplemental material: 3 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.08835 [pdf]
PLB(2022)·11 citations
03
[Submitted on 21 Jan 2022]
Electric and Magnetic Moments and Transition Probabilities in $^{208}$ Pb $\pm 1$ Nuclei
V. Tselyaev · N. Lyutorovich · J. Speth · G. Martinez-Pinedo · K. Langanke · P.-G. Reinhard
We present moments and transition probabilities in the neighboring odd-mass nuclei of $^{208}$ Pb calculated fully self-consistently from the s.p. properties of $^{208}$ Pb with polarization corrections from its excitations, both given from previous Skyrme-Hartree-Fock and RPA calculations. The electric results agree nicely with the data with two very interesting exceptions. In the magnetic case we obtain similar results. We discuss also polarization contributions to the $l$ -forbidden $M 1$ transitions, which are, however, much too small compared to the data. With a modified external field operator which accounts effectively for mesonic and many-body effects the description of the data can be substantially improved.
Comments:
12 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.08838 [pdf]
3 citations

Affiliations

first authorsco-authorsvia INSPIRE

Neutron skin in 48Ca determined from p+48Ca and 48Ca+12C scattering

Controlling extrapolations of nuclear properties with feature selection

Electric and Magnetic Moments and Transition Probabilities in 208Pb ±1 Nuclei

Affiliations

Neutron skin in $^{48}$ Ca determined from p+ $^{48}$ Ca and $^{48}$ Ca+ $^{12}$ C scattering

Electric and Magnetic Moments and Transition Probabilities in $^{208}$ Pb $\pm 1$ Nuclei