The electric dipole moment of the nucleon from simulations at imaginary vacuum angle theta

TL;DR

This paper presents a lattice QCD study of the nucleon electric dipole moment at imaginary theta, utilizing novel boundary conditions to accurately determine CP-odd form factors and test the QCD vacuum structure.

Contribution

It introduces the use of partially twisted boundary conditions in lattice QCD to compute the nucleon electric dipole moment at imaginary theta, providing new insights into CP violation and QCD vacuum properties.

Findings

Successful extraction of the CP-odd form factor F_3 at zero momentum transfer.

Validation of the QCD vacuum structure at nonzero theta.

First lattice QCD calculation of nucleon EDM using this method.

Abstract

We compute the electric dipole moment of proton and neutron from lattice QCD simulations with N_f=2 flavors of dynamical quarks at imaginary vacuum angle theta. The calculation proceeds via the CP odd form factor F_3. A novel feature of our calculation is that we use partially twisted boundary conditions to extract F_3 at zero momentum transfer. As a byproduct, we test the QCD vacuum at nonvanishing theta.