  Metal-insulator transitions in the paramagnetic phase of the two dimensional
square lattice Hubbard model are studied using the dynamical cluster
approximation with eight momentum cells. We show that both the
interaction-driven and the doping-driven transition are multi-stage and
momentum-sector specific, with Fermi liquid metal and fully gapped insulator
phases separated by an intermediate phase in which some regions of the
Brillouin zone are gapped while others sustain gapless quasiparticles. We argue
that this is the coarse-grained version of a gradually shrinking arc or pocket.
A pronounced particle-hole asymmetry is found.
