We study an SU(3) gauge theory with $N_f=8$ degenerate flavors of light fermions in the fundamental representation. Using the domain wall fermion formulation, we investigate the light hadron spectrum, chiral condensate $⟨\overline{\psi }\psi ⟩$ and electroweak $S$ parameter. We consider a range of light fermion masses on two lattice volumes at a single gauge coupling chosen so that IR scales approximately match those from our previous studies of the two- and six-flavor systems. Our results for the $N_f=8$ spectrum suggest spontaneous chiral symmetry breaking, though fits to the fermion mass dependence of spectral quantities do not strongly disfavor the hypothesis of mass-deformed infrared conformality. Compared to $N_f=2$ we observe a significant enhancement of $⟨\overline{\psi }\psi ⟩$ relative to the symmetry breaking scale $F$, similar to the situation for $N_f=6$. The reduction of the $S$ parameter, related to parity doubling in the vector and axial-vector channels, is also comparable to our six-flavor results.

• Received 27 May 2014

DOI:https://doi.org/10.1103/PhysRevD.90.114502