Quark chromoelectric dipole moment operator on the lattice
Tanmoy Bhattacharya (Group T-2, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA); Vincenzo Cirigliano (Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA); Rajan Gupta (Group T-2, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA); Emanuele Mereghetti (Group T-2, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA); Jun-Sik Yoo (Group T-2, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA); et al - Show all 6 authors
We present a lattice QCD study of the contribution of the isovector quark chromoelectric dipole moment (qcEDM) operator to the nucleon electric dipole moments (nEDM). The calculation was carried out on four flavor highly improved staggered quark (HISQ) ensembles generated by the MILC Collaboration. Wilson-clover quarks were used to construct correlation functions. This clover-on-HISQ formulation is not fully improved, and gives rise to additional systematics over and above those due to removing excited state contributions to getting ground-state matrix elements, and the final chiral and continuum extrapolations to get the physical result. We use the nonsinglet axial Ward identity (AWI) including corrections up to to show how to control the power-divergent mixing of the isovector qcEDM operator with the lower-dimensional pseudoscalar operator. The residual corrections are observed to give rise to violations in relations arising from the AWI. We devise three methods attempting to control the resulting uncertainty in the -violating form factor; each of these, however, can have large corrections. Preliminary results for the nEDM due to qcEDM are presented choosing the method giving the most uniform behavior.
