APEC Seminar (Astronomy - Particle Physics - Experimental Physics - Cosmology)

Speaker: Keisuke Harigaya (U Chicago)
Title: A solution to the strong CP problem from mirror QCD and chiral U(1)
Date (JST): Wed, Jul 01, 2026, 13:30 - 15:00
Place: Seminar Room A
Abstract:
We present a solution to the strong CP problem in which a simple chiral U(1) gauge symmetry gives rise to an accidental Peccei-Quinn symmetry. The Peccei-Quinn symmetry is both explicitly and spontaneously broken by mirror QCD dynamics, yielding a framework without an axion quality problem. The model contains no stable domain walls or colored relics, and it accommodates a sufficiently high reheating temperature to account for the baryon asymmetry of the Universe via leptogenesis. Metastable domain walls generate a stochastic background of primordial gravitational waves. Additionally, one of the pseudo-Nambu-Goldstone bosons serves as a viable WIMP dark matter candidate, while colored pseudo-Nambu-Goldstone bosons can be probed at the LHC through searches for jets plus missing energy, multi jets plus leptons, and displaced vertices.