  We explore the Matsubara quasiparticle fraction and the pseudogap of the
two-dimensional Hubbard model with the dynamical cluster quantum Monte Carlo
method. The character of the quasiparticle fraction changes from non-Fermi
liquid, to marginal Fermi liquid to Fermi liquid as a function of doping,
indicating the presence of a quantum critical point separating non-Fermi liquid
from Fermi liquid character. Marginal Fermi liquid character is found at low
temperatures at a very narrow range of doping where the single-particle density
of states is also symmetric. At higher doping the character of the
quasiparticle fraction is seen to cross over from Fermi Liquid to Marginal
Fermi liquid as the temperature increases.
