Research Interests

My research focuses on using high-performance supercomputers to nonperturbatively calculate physical quantities at the quark and gluon level (that is, using quantum chromodynamics or QCD). These strong interactions are directly calculated from the Standard-Model path integral, using a four-dimensional grid in Euclidean spacetime, a theoretical tool known as lattice gauge theory. Using lattice QCD, I am investigating particle properties that will help discern the difference between new physics and the Standard Model in searches at the Large Hadron Collider (LHC) and beyond. This includes the first lattice-QCD calculation of the Bjorken-x dependence of parton distribution functions (PDFs), precision determinations of nucleon properties for new-physics searches in electric dipole moments (EDMs), dark-matter searches, interactions in neutron/nuclear beta decays, and more.

My most recent work on the direct calculation of the Bjorken-x dependence of nucleon parton distribution functions broke through one of the most difficult problems in the lattice hadron-structure calculations. Lattice QCD has long been unable to directly calculate the dependence of hadron structure on Bjorken-x, the fractional momentum carried by partons. I was the first person to achieve this, using a method based on a novel connection: While in the rest frame of the proton, the parton distributions correspond to light-cone correlations, in the infinite-momentum frame, the same distributions correspond to time-independent space correlations. An effective field theory approach taking the infinite-momentum limit can be established, yielding matching conditions that relate finite-momentum lattice data and to the light-cone distribution. Our pioneering study gives access to antiquark structure that could never have been studied in the traditional lattice moment approach. Follow-up work has already been started by other lattice collaborations. The next step forward will be to address the systematic uncertainties in the calculation, such as the matching between continuum and lattice quantities. Improving our knowledge of the PDFs can greatly assist new-physics searches in the upcoming LHC runs, especially for the less-known intrinsic strange and charm contributions. I am also working to probe fundamental symmetries by combining precision low-energy experimental results with SM quantities calculated using lattice QCD. This work is done through the Precision Neutron-Decay Matrix Elements (PNDME) collaboration, of which I was a founding member and principal investigator responsible for getting significant computational resources from US supercomputer centers. We are seeking to improve the nucleon tensor and scalar charges in concert with measurements of the neutron beta-decay parameters to set bounds on new-particle energy scales in the TeV that are competitive with the LHC. My work on light and strange tensor charges has greatly improved our understanding of these inputs, and we use them to set a nEDM limit for split SUSY BSM models.