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Dr Michael Dinmore

Postgraduate Research Student

My publications


M. J Dinmore, N. K Timofeyuk, J. S Al-Khalili (2021)Three-body optical potentials in (d,p) reactions and their influence on indirect study of stellar nucleosynthesis, In: Physical Review C104(3) American Physical Society

Model uncertainties arising due to suppression of target excitations in the description of deuteron scattering and resulting in a modification of the two-body interactions in a three-body system are investigated for several (d,p) reactions serving as indirect tools for studying the astrophysical (p,γ) reactions relevant to rp process. The three-body nature of the deuteron-target potential is treated within the adiabatic distorted-wave approximation (ADWA) which relies on a dominant contribution from the components of the three-body deuteron-target wave function with small n−p separations. This results in a simple prescription for treating the explicit energy dependence of two-body optical potentials in a three-body system requiring nucleon optical potentials to be evaluated at a shifted energy with respect to the standard value of half the deuteron incident energy. In addition, the ADWA allows for leading-order multiple-scattering effects to be estimated, which leads to a simple renormalization of the adiabatic potential's imaginary part by a factor of two. These effects are assessed using both nonlocal and local optical potential systematics for 26Al, 30P, 34Cl, and 56Ni targets at a deuteron incident energy of 12 MeV, which is typical for experiments with radioactive beams in inverse kinematics. The model uncertainties induced by the three-body nature of deuteron-target scattering are found to be within 40% both in the main peak of angular distributions and in total (d,p) cross sections. At higher deuteron energies, around 60 MeV, model uncertainties can reach 100% in the total cross sections. A few examples of application to astrophysically interesting proton resonances in 27Si and 57Cu obtained using (d,p) reactions and mirror symmetry are given.

M. J. Dinmore, N. K. Timofeyuk, J. S. Al-Khalili, R. C. Johnson (2019)Effects of an induced three-body force in the incident channel of (d,p) reactions, In: Physical Review C99(6)064612pp. 064612-1 American Physical Society

A widely accepted practice for treating deuteron breakup in A(d,p)B reactions relies on solving a three-body A+n+p Schrödinger equation with pairwise A−n, A−p and n−p interactions. However, it was shown in Phys. Rev. C 89, 024605 (2014) that projection of the many-body A+2 wave function into the three-body A+n+p channel results in a complicated three-body operator that cannot be reduced to a sum of pairwise potentials. It contains explicit contributions from terms that include interactions between the neutron and proton via excitation of the target A. Such terms are normally neglected. We estimate the first-order contribution of these induced three-body terms and show that applying the adiabatic approximation to solving the A+n+p model results in a simple modification of the two-body nucleon optical potentials. We illustrate the role of these terms for the case of 40Ca(d,p)41Ca transfer reactions at incident deuteron energies of 11.8, 20, and 56 MeV, using several parametrizations of nonlocal optical potentials.

NATALIA TIMOFEYUK, MICHAEL JAMES DINMORE, JIM AL-KHALILI (2020)Three-nucleon force contribution to the deuteron channel in (d, p) reactions, In: Physical Review C102064616 American Physical Society

The contribution of a three-nucleon (3N) force, acting between the neutron and proton in the incoming deuteron with a target nucleon, to the deuteron-target potential in the entrance channel of the A(d, p)B reaction has been calculated within the adiabatic distorted wave approximation (ADWA). Four different 3N interaction sets from local chiral effective field theory (χEFT) at next-to-next-to-leading order (N2LO) were used. Strong sensitivity of the adiabatic deuteron-target potential to the choice of the 3N force format has been found, which originates from the enhanced sensitivity to the short-range physics of nucleon-nucleon (NN) and 3N interactions in the ADWA. Such a sensitivity is reduced when a Watanabe folding model is used to generate d-A potential instead of ADWA. The impact of the 3N force contribution on (d, p) cross sections depends on assumptions made about the p-A and n-A optical potentials used to calculate the distorted d-A potential in the entrance channel. It is different for local and nonlocal optical potentials and depends on whether the induced three-body force arising due to neglect of target excitations is included or not.