Strong CP breaking and quark-antiquark repulsion in QCD, at finite theta

Abstract

This work is devoted to the study of the CP-breaking dynamics in QCD, at finite theta-angle. By working in the semi-classical limit, in which the topology of the vacuum is clustered around instantons and anti-instantons, we show that quantum fluctuations of the theta-vacuum generate an effective flavor-dependent repulsion between matter and anti-matter, inside hadrons. As a consequence, during the tunneling between the degenerate vacua, quarks and anti-quarks in the neutron migrate in opposite directions, giving rise to an oscillating electric dipole moment. We discuss a possible phenomenological implication of this effect.

Final version, accepted for publication on Phys. Rev. D (Rapid Comm.)

References in corpus (1)

• The Neutron Electric Dipole Moment in the Instanton Vacuum: Quenched Versus Unquenched Simulations

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• Parity-odd Parton Distribution Functions from $\theta$-Vacuum
• Tensor supercurrent in QCD