07/16/2026
By Sean Byrne

The Kennedy College of Sciences, Department of Physics, invites you to attend a doctoral dissertation defense by Sean Patrick Byrne on "The 57Ni(p,γ)58Cu Reaction Rate and the νp-Process Through Gamma-Ray Spectroscopy."

Candidate Name: Sean Patrick Byrne
Degree: Doctoral
Defense Date: Thursday, July 30, 2026
Time: 10 to 11:30 a.m.
Location: Room 212, Pinanski Hall, North Campus, UMass Lowell

Thesis/Dissertation Title: Constraining the 57Ni(p,γ)58Cu Reaction Rate for the νp-Process with Coincident γ-Ray Spectroscopy

Committee Members:

  • Advisor: Andrew M. Rogers, Ph.D., Department of Physics and Applied Physics, University of Massachusetts Lowell
  • Partha Chowdhury, Ph.D., Department of Physics and Applied Physics, University of Massachusetts Lowell
  • Ofer Cohen, Ph.D., Department of Physics and Applied Physics, University of Massachusetts Lowell

Brief Abstract:

Understanding the nuclear reactions responsible for the production of elements in explosive astrophysical environments is important for modeling the origin and evolution of matter throughout the universe, including the isotopic abundances incorporated into stellar systems. One reaction of interest is 57Ni(p, γ)58Cu, which plays a role in proton-rich nucleosynthesis pathways associated with the νp-process in core-collapse supernovae, magnetorotational supernovae, and other extreme astrophysical environments. Uncertainties in the nuclear structure of 58Cu, particularly for low-spin states at and above the proton separation energy, contribute directly to uncertainties in thermonuclear reaction rate and nucleosynthesis calculations. To investigate these states, a high-resolution γ-γ coincidence experiment was performed at Argonne National Laboratory’s ATLAS facility using the Gammasphere array and the Neutron Shell detector system. Low-spin states in 58Cu were preferentially populated through the 58Ni(p, n)58Cu reaction using a 17-MeV proton beam. Coincidence spectroscopy, angular correlation measurements, shell model calculations, and mirror-nucleus comparisons were used to construct a revised level scheme and identify resonant states relevant to the astrophysical reaction rate.

The updated spectroscopic information identified 14 previously unreported states, substantially improved the energies and spin constraints of 10 previously known states, and confirmed seven recently reported states from complementary measurements. This revised nuclear structure was incorporated into Monte Carlo thermonuclear reaction-rate calculations. The resulting reaction rate differs relative to the current standard rate over the temperature range relevant to the νp-process, while providing improved experimental constraints on the reaction-rate uncertainty. The updated rate was subsequently implemented in nucleosynthesis network calculations for core-collapse and magnetorotational supernova trajectories to evaluate its impact on the production of nuclei synthesized through the νp-process, including selected isotopes of astrophysical interest. This work demonstrates how precision nuclear structure measurements of 58Cu can significantly constrain the 57Ni(p, γ)58Cu reaction rate and reduce nuclear physics uncertainties in models of explosive nucleosynthesis.