Colorful Mirror Solution to the Strong CP Problem

Abstract

We propose theories of a complete mirror world with parity (P) solving the strong CP problem. P exchanges the entire standard model with its mirror copy. We derive bounds on the two new mass scales that arise: v′ where parity and mirror electroweak symmetry are spontaneously broken, and v3 where the color groups break to the diagonal strong interactions. The strong CP problem is solved even if v3≪v′, when heavy colored states at the scale v3 may be accessible at LHC and future colliders. Furthermore, we argue that the breaking of P introduces negligible contributions to θ¯QCD, starting at three-loop order. The symmetry breaking at v3 can be made dynamical, without introducing an additional hierarchy problem.