  We examine the quasiparticle lifetime and spectral weight near the Fermi
surface in the two-dimensional Hubbard model. We use the FLEX approximation to
self-consistently generate the Matsubara Green's functions and then we
analytically continue to the real axis to obtain the quasiparticle spectral
functions. We compare the spectral functions found in the nearest neighbor
hopping only Hubbard model with those found when second neighbor hopping is
included. This separates the effects of nesting, the Van Hove singularity and
the short-ranged antiferromagnetic correlations. The quasiparticle scattering
rate is enhanced along the (0,pi) to (pi,pi) Brillouin zone diagonal. When the
density is close to half-filling these 'hot-spots' lie on the Fermi surface and
the scattering rate increases with decreasing temperature. For the next-nearest
neighbor hopping scenario we observe a large range of doping where there is no
antiferromagnetism but the scattering rate has a linear temperature dependence.
On decreasing the interaction this non-Fermi liquid behavior is confined to
doping levels where the Fermi energy lies near to the Van Hove singularity. We
conclude that the 'hot-spots' are associated with the antiferromagnetic phase
transition while the linear temperature dependence of the scattering rate is
associated with the Van Hove singularity.
