I am a member of Filomena Nunes's research group at the Facility for Rare Isotope Beams at Michigan State University. We are currently working on the development of theoretical tools to study direct nuclear reactions. 

My graduate school work was on the calculation of microscopic nucleon-nucleus optical potentials based on two- and three-nucleon interactions from chiral effective field theory.  A python script for using the Whitehead-Lim-Holt global optical potential can be downloaded here.

A full list of my publications may be found here: https://inspirehep.net/authors/1621981



Recent Papers




Microscopic global optical potential for rare isotope reactions

T. R. Whitehead, Y. Lim, and J. W. Holt

arXiv:2009.08436

We develop for the first time a microscopic global nucleon-nucleus optical potential with quantified uncertainties suitable for analyzing nuclear reaction experiments at next-generation rare-isotope beam facilities. Within the improved local density approximation and without any adjustable parameters, we begin by computing proton-nucleus and neutron-nucleus optical potentials from a set of five nuclear forces from chiral effective field theory for 1800 target nuclei in the mass range
12 ≤ A ≤ 242 for energies between 0 MeV < E ≲ 150 MeV. We then parameterize a global optical potential for each chiral force that depends smoothly on the projectile energy as well as the target nucleus mass number and isospin asymmetry. Uncertainty bands for elastic scattering observables are generated from a full covariance analysis of the parameters entering in the description of our global optical potential and benchmarked against existing experimental data for stable target nuclei.
Since our approach is purely microscopic, we anticipate a similar quality of the model for nucleonscattering on unstable isotopes.












Neutron elastic scattering on calcium isotopes from chiral nuclear optical potentials

T. R. Whitehead, Y. Lim, and J. W. Holt

PhysRevC.101.064613

We formulate microscopic neutron-nucleus optical potentials from many-body perturbation theory based on chiral two- and three-body forces. The neutron self-energy is first calculated in homogeneous matter to second order in perturbation theory, which gives the central real and imaginary terms of the optical potential. The real spin-orbit term is calculated separately from the density matrix expansion using the same chiral interaction as in the self-energy. Finally, the full neutronnucleus optical potential is derived within the improved local density approximation utilizing mean field models consistent with the chiral nuclear force employed. We compare the results of the microscopic calculations to phenomenological models and experimental data up to projectile energies of E = 200 MeV. Experimental elastic differential scattering cross sections and vector analyzing powers are generally well reproduced by the chiral optical potential, but we find that total cross sections are overestimated at high energies.





Proton elastic scattering on calcium isotopes from chiral nuclear optical potentials

T. R. Whitehead, Y. Lim, and J. W. Holt

PhysRevC.100.014601

We formulate microscopic optical potentials for nucleon-nucleus scattering from chiral two- and three-nucleon forces. The real and imaginary central terms of the optical potentials are obtained from the nucleon self energy in infinite nuclear matter at a given density and isospin asymmetry, calculated self-consistently to second order in many-body perturbation theory. The real spin-orbit term is extracted from the same chiral potential using an improved density matrix expansion. The densitydependent optical potential is then folded with the nuclear density distributions of 40,42,44,48Ca from which we study proton-nucleus elastic scattering and total reaction cross sections using the reaction code TALYS. We compare the results of the microscopic calculations to those of phenomenological models and experimental data up to projectile energies of E = 180 MeV. While overall satisfactory agreement with the available experimental data is obtained, we find that the elastic scattering and total reaction cross sections can be significantly improved with a weaker imaginary optical potential, particularly for larger projectile energies.




Tensor Fermi liquid parameters in nuclear matter from chiral effective field theory

J. W. Holt , N. Kaiser and T. R. Whitehead

PhysRevC.97.054325

We compute from chiral two- and three-body forces the complete quasiparticle interaction in symmetric nuclear matter up to twice nuclear matter saturation density. Second-order perturbative contributions that account for Pauli-blocking and medium polarization are included, allowing for an exploration of the full set of central and noncentral operator structures permitted by symmetries and the long-wavelength limit. At the Hartree-Fock level, the next-to-next-to-leading order threenucleon force contributes to all noncentral interactions, and their strengths grow approximately linearly with the nucleon density up that of saturated nuclear matter. Three-body forces are shown to enhance the already strong proton-neutron effective tensor interaction, while the corresponding like-particle tensor force remains small. We also find a large isovector cross-vector interaction but small center-of-mass tensor interactions in the isoscalar and isovector channels. The convergence of the expansion of the noncentral quasiparticle interaction in Landau parameters and Legendre polynomials is studied in detail.




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