The electric dipole moments (EDM) of the nucleon is a very sensitive probe of CP-violation. The current bound on the neutron EDM strongly constrains many beyond-the-Standard Model (BSM) physics scenarios. With the current experimental accuracy, a non-zero nucleon EDM could not be accounted for by a phase in the quark-mass matrix. This implies that EDM is either caused by a non-zero QCD theta term or by genuine BSM physics which, at low energies, can be parametrized in terms of higher-dimensional CP-violating quark-gluon operators. I will present recent Lattice QCD results for the nucleon EDM induced by the theta term. A key theoretical tool is the Gradient Flow. I will clarify the importance of the Gradient Flow in renormalizing the CP-violating operators, show some selected results and discuss the difficulties and pitfalls that an EDM lattice QCD calculation entails.
Andrea Shindler / Michigan State University
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