Overview
Professor Howell’s research is in the area of experimental nuclear physics with emphasis on the quantum chromodynamics (QCD) description of low-energy nuclear phenomena, including structure properties of nucleons and nuclei and reaction dynamics in few-nucleon systems. The macroscopic properties of nucleon structure and the residual strong nuclear force between neutrons and protons in nuclei emerge from QCD at distances where the color interactions between quarks and gluons are strong. However, the details of the mechanisms that generate the strong nuclear force are not well understood. Effective field theories (EFT) and Lattice QCD calculations provide theoretical frames that connect low-energy nuclear phenomena to QCD. Professor Howell and collaborators are conducting experiments on few-nucleon systems that test predictions of ab-initio theory calculations for the purpose of providing insight about the QCD descriptions of low-energy nucleon interactions and structure. His current projects include measurements of the electromagnetic and spin-dependent structure properties of nucleons via Compton scattering on the proton and few-nucleon systems and studies of two- and three-nucleon interactions using few-nucleon reactions induced by photons and neutrons. In the coming years, a focus will be on investigating the neutron-neutron interaction in reactions and inside nuclei. In addition, his work includes applications of nuclear physics to national nuclear security, medical isotope production, and plant biology. Most of his research is carried out at the High Intensity Gamma-ray Source and the tandem laboratory at TUNL.
Current Appointments & Affiliations
Recent Publications
Energy dependence of chain fission product yields from neutron-induced fission of 235U, 238U, and 239Pu
Journal Article Nuclear Data Sheets · June 1, 2025 The lack of completeness and systematic studies of cumulative fission product yield (FPY) from the three major actinides of 235U, 238U, and 239Pu, over a broad energy range, was the primary motivation for the LLNL-LANL-TUNL ... Full text CitePhotonuclear cross sections for Au 197: An update on the gold standard
Journal Article Physical Review C · December 1, 2024 Cross sections for the Au197(γ,n) reaction are broadly used in nuclear physics as a standard for normalizing photonuclear reaction cross-section data at photon beam energies above approximately 8 MeV. In this paper, we report cross-section measurements for ... Full text CiteUse of the HIFROST Dilution Refrigerator for the T20 Experiment
Conference Proceedings of Science · July 30, 2024 I discussed the importance of the T20 quantity, a tensor analyzing power, and the basic experimental setup for a measurement of ↔ d (γ→, n)p, the deuteron photodisintegration. Multiple measurements have suggested the existence of a channel aroun ... CiteRecent Grants
NEUTRON SCATTERING EXPERIMENTS FOR ACTINIDES USING MONOENERGETIC NEUTRON BEAMS
ResearchPrincipal Investigator · Awarded by Lawrence Livermore National Laboratory · 2025 - 2028Alfred P. Sloan Foundation Graduate School Award
Inst. Training Prgm or CMECo-Principal Investigator · Awarded by Alfred P. Sloan Foundation · 2017 - 2027Studies of Nuclear Structure Using Neutrons and Charged Particles
ResearchCo Investigator · Awarded by Department of Energy · 1997 - 2027View All Grants