Abstract
Effective field theory arguments suggest that if BSM sectors contain new sources of CP-violation that couple to QCD, these sources will renormalize the $\theta$ 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 $\theta$ and the collections of EDMs generated in a 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.
Highlights
The universe violates parity (P) and charge-parity (CP) symmetries
Since we have focused on a limiting case of the minimal supersymmetric standard model (MSSM) where the only phase is in the gluino mass, the electric dipole moment (EDM) phenomenology is dominated by quark EDMs and chromoEDMs
The strong CP problem has been getting worse by about an order of magnitude every decade for the last 60 years [114]
Summary
The universe violates parity (P) and charge-parity (CP) symmetries. In the standard model (SM), the weak interactions break P and CP, while, beyond the standard model, new sources of CP violation are required to generate the baryon asymmetry. The sequestering required to protect θfrom spontaneous P=CP breaking to several loop order typically prevents any other sources of hadronic CP violation—various dimension-six operators, in the language of the SM effective field theory (SMEFT)—from being generated at an observable level. If new sources of strong-sector CP violation are observed, axion solutions to the strong CP problem—which largely relax the IR value of θregardless of its renormalization at intermediate scales and the presence of higher dimension operators—become essentially the only game in town This EFT argument gives low energy EDM experiments a unique and interesting window into the strong CP problem.
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