Search

We have revisited the calculation of the neutron electric dipole moment in the presence of the CP-violating operators up to dimension 5 based on the chiral perturbation theory. In particular, we focus on the contribution of strangeness content. In the calculation, we extract the nucleon matrix elements of scalar-type quark operators from the results of the lattice QCD simulations, while those of the dipole-type quark-gluon operators are evaluated by using the method of the QCD sum rules. As a result, it is found that although the strangeness quantity in nucleons is small, the contribution of the chromoelectric dipole moment of strange quarks may still be sizable, and thus may offer a sensitive probe for the CP-violating interactions in physics beyond the Standard Model. [ABSTRACT FROM AUTHOR]

We elucidate a cancellation mechanism for the electric dipole moment of the electron in the general two Higgs doublet model. The impressive improvement by the ACME Collaboration in 2018 suggests the presence of a new electron Yukawa coupling that brings in exquisite cancellations among dangerous diagrams, broadening the solution space for electroweak baryogenesis driven by an extra top Yukawa coupling. The cancellation mechanism calls for the new Yukawa couplings to have hierarchical structures that echo the observed pattern of the Standard Model Yukawa couplings. [ABSTRACT FROM AUTHOR]

Effective field theory arguments suggest that if beyond the standard model (BSM) sectors contain new sources of CP violation that couple to QCD, these sources will renormalize the θ term and frustrate ultraviolet solutions to the strong CP problem. Simultaneously, they will generate distinctive patterns of low-energy electric dipole moments in hadronic, nuclear, atomic, and molecular systems. Observing such patterns thus provides evidence that strong CP is solved by an infrared relaxation mechanism. We illustrate the renormalization of θ and the collections of electric dipole moments generated in several models of BSM physics, confirming effective field theory expectations, and demonstrate that measurements of ratios of electric dipole moments at planned experiments can provide valuable input on the resolution of the strong CP problem. [ABSTRACT FROM AUTHOR]

In the standard model, the renormalization of the QCD vacuum angle θ is extremely tiny, and small θ is technically natural. In the general standard model effective field theory (SMEFT), however, Δθ is quadratically divergent, reflecting the fact that new sources of hadronic CP-violation typically produce O (1) threshold corrections to θ. The observation of such CP-violating interactions would therefore be in tension with solutions to the strong CP problem in which θ = 0 is an ultraviolet boundary condition, pointing to the Peccei-Quinn mechanism as the explanation for why θ is small in the infrared. We study the quadratic divergences in θ arising from dimension-6 SMEFT operators and discuss the discovery prospects for these operators at electric dipole moment experiments, the LHC, and future proton-proton colliders. [ABSTRACT FROM AUTHOR]