2010/03/04 by Clifford Cheung
Physics and Astronomy · #Axion #CP violation #Dark Matter and Cosmic Phenomena #Fermion #Operator (biology) #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quark #Strong CP problem #Symmetry breaking #Yukawa potential #hep-ph #hep-th
paper · pdf · doi:10.1007/jhep06(2010)074
published as JHEP 1006:074,2010 · 16 pages, 2 figures
arxiv created 2010/03/04 · openalex publication_date 2010/06/01 · arxiv updated 2014/11/20 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The QCD axion fails to solve the strong CP problem unless all explicit PQ violating, Planck-suppressed, dimension n < 10 operators are forbidden or have exponentially small coefficients. We show that all theories with a QCD axion contain an irreducible source of explicit PQ violation which is proportional to the determinant of the Yukawa interaction matrix of colored fermions. Generically, this contribution is of low operator dimension and will drastically destabilize the axion potential, so its suppression is a necessary condition for solving the strong CP problem. We propose a mechanism whereby the PQ symmetry is kept exact up to n = 12 with the help of the very same flavor symmetries which generate the hierarchical quark masses and mixings of the SM. This “axion flavor protection” is straightforwardly realized in theories which employ radiative fermion mass generation and grand unification. A universal feature of this construction is that the heavy quark Yukawa couplings are generated at the PQ breaking scale.