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Title: Optical potential from first principles

Here, we develop a method to construct a microscopic optical potential from chiral interactions for nucleon-nucleus scattering. The optical potential is constructed by combining the Green’s function approach with the coupled-cluster method. To deal with the poles of the Green’s function along the real energy axis we employ a Berggren basis in the complex energy plane combined with the Lanczos method. Using this approach, we perform a proof-of-principle calculation of the optical potential for the elastic neutron scattering on 16O. For the computation of the ground-state of 16O, we use the coupled-cluster method in the singles-and-doubles approximation, while for the A ±1 nuclei we use particle-attached/removed equation-of-motion method truncated at two-particle-one-hole and one-particle-two-hole excitations, respectively. We verify the convergence of the optical potential and scattering phase shifts with respect to the model-space size and the number of discretized complex continuum states. We also investigate the absorptive component of the optical potential (which reflects the opening of inelastic channels) by computing its imaginary volume integral and find an almost negligible absorptive component at low-energies. To shed light on this result, we computed excited states of 16O using equation-of-motion coupled-cluster method with singles-and- doubles excitations and we found no low-lying excited statesmore » below 10 MeV. Furthermore, most excited states have a dominant two-particle-two-hole component, making higher-order particle-hole excitations necessary to achieve a precise description of these core-excited states. We conclude that the reduced absorption at low-energies can be attributed to the lack of correlations coming from the low-order cluster truncation in the employed coupled-cluster method.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [3]
  1. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Laboratory (NSCL)/ Facility for Rare Isotope Beams (FRIB) Lab.; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Joint Institute for Nuclear Physics and Applications (JINPA)
  2. Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Laboratory (NSCL)/ Facility for Rare Isotope Beams (FRIB) Lab.; Michigan State Univ., East Lansing, MI (United States).l Dept. of Physics and Astronomy
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Physics Division; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
Publication Date:
Grant/Contract Number:
NA0002132; FG02-96ER40963; FG52-08NA28552; SC0008499; AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 95; Journal Issue: 2; Journal ID: ISSN 2469-9985
Publisher:
APS
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP) (NA-10); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
OSTI Identifier:
1357089
Alternate Identifier(s):
OSTI ID: 1344012; OSTI ID: 1394459

Rotureau, J., Danielewicz, P., Hagen, G., Nunes, F. M., and Papenbrock, T.. Optical potential from first principles. United States: N. p., Web. doi:10.1103/PhysRevC.95.024315.
Rotureau, J., Danielewicz, P., Hagen, G., Nunes, F. M., & Papenbrock, T.. Optical potential from first principles. United States. doi:10.1103/PhysRevC.95.024315.
Rotureau, J., Danielewicz, P., Hagen, G., Nunes, F. M., and Papenbrock, T.. 2017. "Optical potential from first principles". United States. doi:10.1103/PhysRevC.95.024315. https://www.osti.gov/servlets/purl/1357089.
@article{osti_1357089,
title = {Optical potential from first principles},
author = {Rotureau, J. and Danielewicz, P. and Hagen, G. and Nunes, F. M. and Papenbrock, T.},
abstractNote = {Here, we develop a method to construct a microscopic optical potential from chiral interactions for nucleon-nucleus scattering. The optical potential is constructed by combining the Green’s function approach with the coupled-cluster method. To deal with the poles of the Green’s function along the real energy axis we employ a Berggren basis in the complex energy plane combined with the Lanczos method. Using this approach, we perform a proof-of-principle calculation of the optical potential for the elastic neutron scattering on 16O. For the computation of the ground-state of 16O, we use the coupled-cluster method in the singles-and-doubles approximation, while for the A ±1 nuclei we use particle-attached/removed equation-of-motion method truncated at two-particle-one-hole and one-particle-two-hole excitations, respectively. We verify the convergence of the optical potential and scattering phase shifts with respect to the model-space size and the number of discretized complex continuum states. We also investigate the absorptive component of the optical potential (which reflects the opening of inelastic channels) by computing its imaginary volume integral and find an almost negligible absorptive component at low-energies. To shed light on this result, we computed excited states of 16O using equation-of-motion coupled-cluster method with singles-and- doubles excitations and we found no low-lying excited states below 10 MeV. Furthermore, most excited states have a dominant two-particle-two-hole component, making higher-order particle-hole excitations necessary to achieve a precise description of these core-excited states. We conclude that the reduced absorption at low-energies can be attributed to the lack of correlations coming from the low-order cluster truncation in the employed coupled-cluster method.},
doi = {10.1103/PhysRevC.95.024315},
journal = {Physical Review C},
number = 2,
volume = 95,
place = {United States},
year = {2017},
month = {2}
}