Oliver Gorton

Postdoctoral Research Staff
Nuclear Data and Theory Group
Lawrence Livermore National Laboratory

Github
Google Scholar
ORC ID: 0000-0003-3643-9640

Interests • Education • Experience
Service • Training
Codes • Publications • Presentations

Shell model dimensions

Research

I develop theory and codes to improve our understanding of nuclear physics as it relates to astrophysics and nuclear technologies, two fields which test our understanding of matter in neutron-rich environments.

Fundamental nuclear physics: advancing the nuclear structure and reaction theory which gov- erns the interaction of neutrons and radiation with matter.

Nuclear data: strengthening nuclear data libraries with physics models and robust uncertainty quantification to empower inference from multi-physics simulations.

High energy-density (HED) science: learning to run HYDRA simulations of NIF implosions to investigate utility of future HED facilities for national security.

Education

• Ph.D. Computational Science, 2024
  “Shell Model Methods, Statistical Nuclear Reactions, and Beta-delayed Neutron Emission”
  University of California, Irvine
  San Diego State University joint doctoral program
  
• M.S. Physics, 2018
  “Efficient Modeling of Nuclei Through Coupling of Proton and Neutron Wavefunctions”
  San Diego State University
  
• B.A. Physics, 2016
  University of California, Berkeley

Experience

• Postdoctoral Research Staff, 2024 – present
  Nuclear Data and Theory Group, Lawrence Livermore National Laboratory (LLNL)
  • Investigating the effects of fundamental nuclear physics uncertainty on neutron-capture rates, and the resulting impact on astrophysical formation of heavy elements
  • Developing theory and codes to model radiative decay of highly-excited nuclei
  • Developing and applying robust statistical inference tools to bolster LLNL nuclear data libraries
• Weapon Physics and Design ACT Scholar, 2022 – 2024
  Nuclear Data and Theory Group, LLNL
  New predictive capability for reaction and decay properties of fission fragments:
  • Proposed solution for under-prediction of beta-delayed photons from fission fragments
  • Combined shell model and Hauser-Feshbach calculations to model beta-delayed reactions
  • Wrote shell model code PANASh (weak-entanglement approximation) to reduced compute costs
  • Devised approximation of Porter-Thomas fluctuations for modeling beta-delayed processes
  • 5 publications, 5 conference talks, defended Ph.D. dissertation at LLNL
• Glenn T. Seaborg Institute (GTSI) Graduate Intern, Summer 2021
  Nuclear Data and Theory Group, LLNL
  • Applied statistical inference code to analyze reaction experiment, resulting in publication
  • Supported machine learning effort for surrogate reaction analysis, resulting in proceedings
• High Energy Density Physics Graduate Intern, Summer 2018, 2019, and 2020
  Nuclear Data and Theory Group, LLNL
  • Developed statistical inference code COMMCAS for nuclear data, resulting in proceedings
  • Demonstrated theoretical limitations of experimental technique, resulting in publication
  • Identified bugs and performance improvements for LLNL nuclear reaction code, YAHFC
• Graduate Teaching Associate, 2016 – 2020
  Department of Physics, San Diego State University
  • Independently taught undergraduate physics lab-courses
  • Co-authored the department manual for Physics 182A/195L laboratory courses

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Service

Service and outreach activities:

• Coding Mentor for “Coding with LLNL” at Christensen Middle School, 2025-26
• Co-organizer for CENTAUR 2026 meeting at LLNL
• LLNL Institutional Computing Grand Challenge Committee Fall 2025
• Referee for Physical Review C

Training

Selected workshops and formal training attendance:

• “Making the most of your presentation” training by Jean-Luc Doumont (2025)
• “FIESTA 2024”, Fission Experiments and Theoretical Advances (FIESTA), a fission-focused school and workshop at LANL
• “Technical Writing Workshop” at LLNL (2019)

Codes

I am the primary developer of these codes:

• COMMCAS Python [LLNL-TR-2011377] [Not yet public]
  Uncertainty quantification and statistical inference framework for nuclear physics models
  • Monte-Carlo, Importance Sampling, MCMC, forward propagation methods
  • Provides generic model wrapper with user-friendly abstractions of model inputs/outputs, experimental data, unknown sources of uncertainty, and more
• PANASh Fortran [Publication] [Not yet public]
  Shell model code with advanced basis-reduction scheme to compute nuclear wave functions
  • Custom Krylov-subspace algorithms (block Lanczos with on-the-fly matrix elements)
  • MPI and openMP hybrid parallelization
• dmscatter Fortran and Python [Publication] [Repository]
  A fast Fortran code for WIMP-nucleus form factors and differential event rate spectra. Modern Fortran with Python interface. OpenMP parallel.
• Wigner Fortran Repository
  A library of functions for computing vector-coupling coefficients, written in modern Fortran.

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Publications

21 publications (9 journal papers, 8 conference proceedings, 4 technical reports)

Journal papers

• Radiative strength functions from the energy-localized Brink-Axel hypothesis
  O. Gorton, K. Kravvaris, J. Escher, C. Johnson
  [Editor’s Suggestion] – Physical Review C 113, 044327 (2026) | arXiv:2601.12225
• Constraining capture cross sections using proton inelastic scattering as a surrogate reaction
  A. Thapa, J. Escher, E. Chimanski, O. Gorton, M. Dupuis, E.J. In, S. Ota, S. Peru, W. Younes
  Physics Letters B 876, 140322 (2026) | arXiv:2511.03071
• Correlated and uncorrelated Monte Carlo neutron capture rate variations in weak r-process simulations
  A. Kedia, J. Berryman, J. Garcia, J. Escher, O. Gorton, E. Holmbeck, G. McLaughlin, C. Pruitt, A. Sieverding, R. Surman
  Submitted to Physical Review C | arXiv:2602.12428
• Towards shell model interactions with credible uncertainties
  O. C. Gorton and K. Kravvaris
  Physical Review C 112, 014302 (2025) | arXiv:2503.11889
• Weak entanglement approximation for nuclear structure
  O. C. Gorton and C. W. Johnson
  Physical Review C 110, 034305 (2024) | arXiv:2406.10120
• Proton-neutron entanglement in the nuclear shell model
  C. W. Johnson and O. C. Gorton
  Journal of Physics G: Nuclear and Particle Physics 50 (4) 045110 (2023) | arXiv:2210.14338
• dmscatter: A fast program for WIMP-nucleus scattering
  O. Gorton, C. Johnson, C. Jiao, J. Nikoleyczik
  Computer Physics Communications 284, 108597 (2023) | arXiv:2209.09187
• Cross sections for neutron-induced reactions from surrogate data: Reexamining the Weisskopf-Ewing approximation for (n,n’) and (n,2n) reactions
  O. C. Gorton and J. E. Escher
  Physical Review C: Nuclear Physics 107 (4), 044612 (2023) | arXiv:2102.03452
• Measurements of proton capture in the A=100-110 mass region: Constraints of the 111In(gamma,p)/(gamma,n) branching point relevant to the gamma-process
  O. Olivas-Gomez, A. Simon, O. Gorton, J. E. Escher et al. 
  Physical Review C: Nuclear Physics 102 (5), 055806 (2020)

Conference papers

• From credible shell model interactions to neutron-capture uncertainties
  O. Gorton and K. Kravvaris
  To be submitted European Physical Journal, Web of Conferences (2026) | arXiv:2604:09935
• A weak entanglement approximation for nuclear structure: a progress report
  C. Johnson and O. Gorton
  Journal of Subatomic Particles and Cosmology, 100061 (2025) | arXiv:2504.00273
• Correcting for neutron width fluctuations in Hauser-Feshbach gamma branching ratios
  O. Gorton and J. Escher
  EPJ Web of Conferences 322, 02004 (2025) | arXiv:2410.01074
• Extending the Dispersive Optical Model to Beta-unstable Systems
  C. Pruitt, S. S. Perrotta, J. Escher, O. Gorton
  EPJ Web of Conferences 322, 05001 (2025)
• Towards next-generation optical potentials for nuclear reactions and structure calculations
  S. S. Perrotta, C. Priutt, O. Gorton, and J. Escher
  Nuclear Physics A 1057, 123037 (2025) | arXiv:2410.19269
• A Problem in the Statistical Description of Beta-Delayed Neutron Emission
  O. Gorton, C. Johnson, and J. Escher
  EPJ Web of Conferences 284, 03013 (2023) | arXiv:2210.05904
• Improving nuclear data evaluations with predictive reaction theory and indirect measurements
  J. Escher, K. Bergstrom, E. Chimanski, O. Gorton, E. J. In, M. Kruse, S. Peru, C. Pruitt, R. Rahman, E. Shinkle, A. Thapa, W. Younes
  EPJ Web of Conferences 284, 03012 (2023) | arXiv:2304:10034
• Neutron capture cross sections from surrogate reaction data and theory: connecting the pieces with a Markov-Chain Monte Carlo approach
  O. Gorton and J. E. Escher
  Springer Proceedings in Physics, vol 254, pages 229-231 (2021) | arXiv:1905:03055

Technical reports

• From new measurements to new data libraries: The LLNL nuclear data pipeline at work M. Anastasiou, B. Beck, R. Casperson, M.-A. Descalle, J. Escher, O. Gorton, K. Kravvaris, C. Mattoon, M. Mendenhall, W. Ormand, G. Potel Aguilar, S. Quaglioni, A. Sieverding, L. Snyder, I. Thompson, and K. Wendt
  Internal working document
• COMMCAS: Computational Model Monte Carlo Sampler
  O. Gorton, J. Escher, S. Perrotta, C. Pruitt, A. Thapa, V. Kruse, E. Shinkle, M. Paik, and H. Frye
  LLNL-TR-2011377-DRAFT
• Evaluations for neutron-induced activation cross sections for Y and Zr isotopes
  A. Sieverding, R. Hoffman, O. Gorton, and W. Ormand
  LLNL-TR-2011750
• Computational Workflows for Uncertainty-Quantified Nuclear Reactions
  J. Berryman, C. Pruitt, J. Escher, O. Gorton, E. M. Holmbeck, K. Kravvaris, A. Sieverding, et al.
  LLNL-TR-2015691
• Final Technical Report: New predictive capability for reaction and decay properties of fission fragments (ACT University Program)
  O. Gorton, H. Frye, C. Johnson, and J. Escher
  LLNL-MI-2003179 (Internal report avilable upon request)

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Presentations

2 invited talks, 17 contributed talks, 6 posters

Invited talks

• Reduced-order models to accelerate uncertainty quantification: from shell model to neutron capture
  O. Gorton
  FRIB-TA Topical Program: Statistical Nuclear Properties in the AI/ML Era: Advances, Chal- lenges, and Synergies for FRIB Science – East Lancing, Michigan, Scheduled July 2026
• Radiative strength functions from the energy-localized Brink-Axel hypothesis
  O. Gorton
  10th Workshop on Level Densities and Gamma Strengths – Oslo, Norway, Scheduled May 2026

Contributed talks

• Nuclear theory for astrophysics and nuclear technologies
  O. Gorton
  PLS Directorate Postdoctoral Seminar (LLNL, February 2026)
  
• Radiative strength functions from the energy-localized Brink-Axel hypothesis
  O. Gorton, K. Kravvaris, J. Escher, C. Johnson
  Talk at the 8th International Conference on Collective Motion in Nuclei under Extreme Conditions (Tallahassee, December 2025)
  
• Shell model for astrophysics and nuclear technologies
  O. Gorton
  Talk at 16th Nuclear Data for Science and Technology Conference (Madrid, June 2025)
  
• Is the USDB interaction unique?
  O. Gorton
  Talk at APS Global Physics Summit (Anaheim, March 2025)
  
• A weak entanglement approximation for nuclear structure
  O. Gorton and C. Johnson
  Talk at Shell Model Symposium: Celebrating 75 Years of the Nuclear Shell Model and Maria Goeppert-Mayer (Argonne National Lab., July 2024)
  
• Missing gammas: beta-delayed neutron emission of Rb-94
  O. Gorton, C. Johnson, J. Escher
  Talk at APS April 2024 Meeting (Sacramento, April 2024)
  
• Gamma-ray strength functions using approximate shell model calculations
  O. Gorton, C. Johnson, J. Escher
  Talk at T3 “Taking the Temperature” Workshop on Statistical Nuclear Physics for Astrophysics and Applications (Ohio University, August 2023)
• Nuclear Shell Model to the Rescue: Efforts to Resolve a Mystery in Beta Delayed Neutron Emission
  O. Gorton, C. Johnson, J. Escher
  Talk at APS Division of Nuclear Physics Fall 2022 Meeting (New Orleans, October 2022)
• Crisis in Beta-Delayed Neutron Emission: Shell Model to the Rescue
  O. Gorton, C. Johnson, J. Escher
  Talk at Nuclear Data Conference (Sacramento – virtual, July 2022)
• DMFortFactor: A Fast and Accessible for Computing WIMP-Nucleus-Scattering Event-Rates
  O. Gorton, C. Johnson, C. Jiao
  Talk at DNP21 APS Conference (Boston – virtual, October 2021)
• Better MCMC for Nuclear Data using emcee and B-DJINN
  O. C. Gorton, J. E. Escher, K. O. Bergstrom, M. K. Kruse
  Talk at LLNL Summer Slam (Livermore, August 2021)
• Nuclear Physics for WIMPs
  O. Gorton and C. W. Johnson
  Talk at SDSU SIAM Student Chapter Summer Colloquium Series, (San Diego, July 2021)
• Cross subsections for neutron reactions from surrogate measurements: Revisiting the Weisskopf-Ewing approximation
  O. Gorton and J. E. Escher
  Talk at DNP20 APS Conference (New Orleans – virtual, October 2020)
• Can we get rid of the theorists?
  O. Gorton and J. E. Escher
  Talk at LLNL Summer Slam (Livermore, August 2020)
• Big Picture and Background for Nuclear-Electronic Orbital (NEO) Approach: Calculating Mixed Nucleon-Electron Wave Functions
  O. Gorton
  Seminar for the Furche Group, Chemistry Department, UC Irvine (Irvine, March 2020)
• Indirect measurements of nuclear cross subsections: tempering experimental results with theory
  O. Gorton and J. E. Escher
  Seminar for HEDP Intern Exit Talk (Livermore, September 2019)
• A Markov Chain Monte Carlo Tool for Hauser-Feshbach Codes
  O. Gorton and J.E. Escher
  Seminar for HEDP Intern Exit Talk (Livermore, August 2018)

Posters

• Width Fluctuation Correction Factor for Beta-delayed Neutron Emission
  O. Gorton, J. Escher
  Poster at the 7th international workshop on Compound-Nuclear Reactions and Related Topics (Vienna, July 2024)
• Proton and Neutron Approximate Shell Model: Factorization-based Importance Truncation
  O. Gorton, C. Johnson, J. Escher
  Poster at Nuclear Structure Conference (Berkeley, June 2022)
• Sensitivity Study of the Surrogate Method
  O. Gorton and J. E. Escher
  Poster at LLNL Student Poster Symposium (Livermore, August 2019)
• Temperature and Entropy in the Nuclear Shell Model
  O. Gorton and C. W. Johnson
  Poster at SDSU ACCESS event (San Diego, April 2019)
• Proton Neutron Interacting Shell Model: Order of Magnitude Reduction for Medium Mass Nuclei
  O. Gorton and C. Johnson
  Poster at SDSU annual research symposium (San Diego, March 2019)
• Neutron capture cross subsections from surrogate reaction data and theory: connecting the pieces with a Markov-Chain Monte Carlo approach
  O. Gorton and J. E. Escher
  Poster at Compound Nuclear Reactions conference CNR18 (Berkeley, September 2018)

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