Nucleon Electric Dipole Moments using Lattice Gauge Theory

The standard model of particle physics agrees remarkably well with most experimental results, and yet, is in violent contradiction with our cosmological models: the universe seems too homogeneous and isotropic on large scales, too clumpy on smaller scales and has altogether too much matter. To have a coherent picture of our universe requires us to look for physics beyond the standard model (BSM). One of the most fruitful places to look for this is by studying a very weakly broken symmetry of the standard model: that of invariance under simultaneous charge conjugation and parity flip (CP)—a symmetry that prohibits electric dipole moments (EDMs) of systems with no near-degenerate excitations. A number of experiments are, therefore, looking for EDMs of neutrons and protons and their current limits are squarely in the range that is informative of new physics just beyond the weak scale. Using an effective field theory language, we can parameterize the leading effects of BSM theories in terms of coefficients of CP-violating dimension-5 and 6 operators. In recent years, simulations of lattice Quantum Chromodynamics (QCD) have attempted to evaluate the matrix elements of many of these operators, with mixed success. In this presentation, we will discuss relevant work from our collaboration.