Abstract
Abstract
A global U(1)PQ symmetry is protected from gravitational effects in the s-confining SU(N)
k
product group theory with
$$ A + 4Q+N\overline{Q} $$
A
+
4
Q
+
N
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) × U(1)PQ → 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
$$ \overline{\theta}<1{0}^{-10} $$
θ
¯
<
1
0
−
10
, even under the pessimistic assumption that the dominant contribution to the axion quality is at tree level.
Publisher
Springer Science and Business Media LLC
Subject
Nuclear and High Energy Physics
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