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Title: Exploring experimental conditions to reduce uncertainties in the optical potential

Abstract

Uncertainty quantification for nuclear theories has gained a more prominent role in the field, with more groups attempting to understand the uncertainties in their calculations. However, recent studies have shown that the uncertainties on the optical potentials are too large for the theory to be useful. The goal of this work is to explore possible experimental conditions that may reduce the uncertainties on elastic scattering and single-nucleon transfer cross sections that come from the fitting of the optical model parameters to experimental data. Using Bayesian methods, we explore the effect of the uncertainties of optical model parameters on the angular grid of the differential cross section, including cross-section data at nearby energies, and changes in the experimental error bars. We also study the effect on the resulting uncertainty when other observables are included in the fitting procedure, particularly the total (reaction) cross sections. We study proton and neutron elastic scattering on 48Ca and 208Pb. We explore the parameter space with the Markov-chain Monte Carlo method, produce posterior distributions for the optical model parameters, and construct the corresponding 95% confidence intervals on the elastic-scattering cross sections. We also propagate the uncertainties on the optical potentials to the 48Ca(d,p) 49Ca(g.s.) and 208Pb(d,p)more » 209Pb(g.s.) cross sections. We find little sensitivity to the angular grid and an improvement of up to a factor of 2 on the uncertainties by including data at a nearby energy. Although reducing the error bars on the data does reduce the uncertainty, the gain is often considerably smaller than one would naively expect. We also find that the inclusion of total reaction cross section can improve the uncertainty although the magnitude of the effect depends strongly on the cases considered.« less

Authors:
 [1];  [1]; ORCiD logo [2];  [1]
  1. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab.
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1601625
Report Number(s):
[LA-UR-19-29248]
[Journal ID: ISSN 2469-9985; PRVCAN]
Grant/Contract Number:  
[89233218C; NA000001]
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
[ Journal Volume: 100; Journal Issue: 6]; Journal ID: ISSN 2469-9985
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
uncertainty quantifi cation; nucleon elastic scattering; transfer nuclear reactions; optical potential fi tting

Citation Formats

Catacora-Rios, Manuel, King, Garrett B., Lovell, Amy Elizabeth, and Nunes, F. M. Exploring experimental conditions to reduce uncertainties in the optical potential. United States: N. p., 2019. Web. doi:10.1103/PhysRevC.100.064615.
Catacora-Rios, Manuel, King, Garrett B., Lovell, Amy Elizabeth, & Nunes, F. M. Exploring experimental conditions to reduce uncertainties in the optical potential. United States. doi:10.1103/PhysRevC.100.064615.
Catacora-Rios, Manuel, King, Garrett B., Lovell, Amy Elizabeth, and Nunes, F. M. Mon . "Exploring experimental conditions to reduce uncertainties in the optical potential". United States. doi:10.1103/PhysRevC.100.064615.
@article{osti_1601625,
title = {Exploring experimental conditions to reduce uncertainties in the optical potential},
author = {Catacora-Rios, Manuel and King, Garrett B. and Lovell, Amy Elizabeth and Nunes, F. M.},
abstractNote = {Uncertainty quantification for nuclear theories has gained a more prominent role in the field, with more groups attempting to understand the uncertainties in their calculations. However, recent studies have shown that the uncertainties on the optical potentials are too large for the theory to be useful. The goal of this work is to explore possible experimental conditions that may reduce the uncertainties on elastic scattering and single-nucleon transfer cross sections that come from the fitting of the optical model parameters to experimental data. Using Bayesian methods, we explore the effect of the uncertainties of optical model parameters on the angular grid of the differential cross section, including cross-section data at nearby energies, and changes in the experimental error bars. We also study the effect on the resulting uncertainty when other observables are included in the fitting procedure, particularly the total (reaction) cross sections. We study proton and neutron elastic scattering on 48Ca and 208Pb. We explore the parameter space with the Markov-chain Monte Carlo method, produce posterior distributions for the optical model parameters, and construct the corresponding 95% confidence intervals on the elastic-scattering cross sections. We also propagate the uncertainties on the optical potentials to the 48Ca(d,p)49Ca(g.s.) and 208Pb(d,p)209Pb(g.s.) cross sections. We find little sensitivity to the angular grid and an improvement of up to a factor of 2 on the uncertainties by including data at a nearby energy. Although reducing the error bars on the data does reduce the uncertainty, the gain is often considerably smaller than one would naively expect. We also find that the inclusion of total reaction cross section can improve the uncertainty although the magnitude of the effect depends strongly on the cases considered.},
doi = {10.1103/PhysRevC.100.064615},
journal = {Physical Review C},
number = [6],
volume = [100],
place = {United States},
year = {2019},
month = {12}
}

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