Lattice QCD with eight Hght-quark flavors

QCD with eight flavors is studied on ${16}^3\times N_t$ lattices with $N_t=4,6, \mathrm{and} 8$, a dynamical quark mass $ma=0.015\mathrm{}$, and lattice coupling $\beta =\frac{6}{g^2}$ between 4.5 and 5.0. For $N_t=16\mathrm{}$, hadron masses and screening lengths are computed for a variety of valence quark masses. The previously observed, strong, first-order transition for $N_t=4,6, \mathrm{and} 8$ is seen, for $N_t=16\mathrm{}$, to become a $\beta$-independent, zero-temperature transition characterized by a factor of ≅ 3 change in lattice scale. This strong, first-order transition restores chiral symmetry, at least for $N_t=4,6, \mathrm{and} 8$, producing a chirally symmetric, weak-coupling phase. However, as $N_t$ increases to 16, the chiral-symmetry properties of the weak-coupling side of the zero-temperature transition are unclear and offer a hint of a normal, finite-temperature, chiral-symmetry-breaking transition in the weak-coupling phase.