A Composite Axion from a Supersymmetric Product Group
arXiv:1707.04261 · doi:10.1007/JHEP11(2017)005
Abstract
A global $U(1)_\text{PQ}$ symmetry is protected from gravitational effects in the s-confining $SU(N)^k$ product group theory with $A+4Q +N\overline{Q}$ matter. If the $SU(4)$ family symmetry is gauged and an appropriate tree-level superpotential is added, then the dynamically generated superpotential spontaneously breaks $SU(4)\times U(1)_\text{PQ} \rightarrow SU(3)_c$ and produces a QCD axion. Small values of the $CP$-violating $θ$ parameter are then possible without any fine-tuning, as long as the product group is suitably large. By introducing a second copy of the s-confining $SU(N)$ product group also coupled to the gauged $SU(4)$, we find that values as small as $N=7$ are consistent with $\barθ<10^{-10}$, even under the pessimistic assumption that the dominant contribution to the axion quality is at tree level.
16 pages, 3 figures, 4 tables, 2 appendices