Electroweak reactions in Low-energy Nuclear Physics

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

Many important reactions in nuclear physics cannot be measured with currently available experimental techniques. For example, the reaction probability of the process in which two protons fuse to form a Deuteron (a bound state of a neutron and a proton) is an important process in the sun, but cannot be measured experimentally; only theoretical calculations can provide this rate. In the absence of guidance from experiment, it becomes important to quantify theoretical uncertainties. This project will address these issues for specific reactions. Analytical and numerical calculations will be used to determine reaction rates for astrophysically-relevant reaction rates, and new parametrizations of the internuclear interaction will be provided. Specifically, the PI and his students will use interactions that have been constructed using a theoretical tool known as effective field theory. This tool is an expansion that can be systematically improved by introducing, in a controlled manner, additional parameters to increase the accuracy of the interaction model. Numerical techniques will be used to determine the intrinsic error of this approach, parametrize the interaction, and calculate the reaction rates for selected processes. A quantification of resulting uncertainties will improve our understanding of the internuclear interaction. This project will also provide an excellent training ground for graduate and undergraduate students and will contribute to a needed workforce in those technologies that rely on nuclear physics, which are relevant to security, energy and the health care sector. Graduate students will become familiarized with numerical methods that can be useful when working in industry. This project follows a two-prong strategy that aims at improving our understanding of weak processes using effective field theory. Firstly, a number of weak processes in few-nucleon systems will be calculated within the unified framework of the so-called pionless effective field theory. Specifically, the well-measured decay half-life time of tritium will be treated and used to fix a parameter that within this framework is required for a high-accuracy of proton-proton fusion and weak proton capture on Helium-3. The second prong will focus on understanding the intrinsic error of Hamiltonians and associated electroweak currents generated with the so-called pionfull effective field theory. The PI will use novel numerical optimization/fitting techniques to establish an ordering scheme for the chiral potential and the associated electroweak currents that reflects the intrinsic error of the Hamiltonian order-by-order. Together with his collaborators, the PI will then use these results to calculate observables such as half-life times or total decay rates to new accuracy and with correct error estimates. The resulting interactions and currents will be made available to the nuclear theory community.