Understanding lattice QCD applications to the two-nucleon system — André Walker-Loud

Lattice QCD offers the promise to quantitatively connect our understanding of low-energy nuclear physics to the Standard Model of particle physics. Such a connection is important for assisting with a broad range current and planned experiments such as the search for permanent EDMs in nuclei, the search for neutrinoless double beta decay, understanding the nuclear response of nuclei to a neutrino beam and possibly, constraining the nuclear equation of state by improving our understanding of the three-nucleon and hyperon-nucleon interactions. Yet, even the calculation of the two-nucleon scattering phase shifts has proved to be extremely challenging with growing tension in the literature on whether two-nucleons, at unphysically heavy pion masses, for bound di-neutron systems.

The resolution of this discrepancy is critical to provide confidence to the broader community that lattice QCD can be a reliable tool for nuclear physics. It will also inform us which of the various calculational methods being used can be relied upon to deliver the correct results, and which ones are susceptible to currently unquantified systematic uncertainties. I will describe how the two-nucleon lattice QCD calculations are performed including the various challenges we face. I will then review the two-nucleon controversy, and finally, I will present progress we are making to resolve the issue.

Recording of the virtual NSCL/FRIB Nuclear Theory Seminar - Feb 16, 2021

Speaker: André Walker-Loud
Lawrence Berkeley National Laboratory