  We introduce a valence-bond dynamical mean-field theory of doped Mott
insulators. It is based on a minimal cluster of two orbitals, each associated
with a different region of momentum space and hybridized to a self-consistent
bath. The low-doping regime is characterized by singlet formation and the
suppression of quasiparticles in the antinodal regions, leading to the
formation of Fermi arcs. This is described in terms of an orbital-selective
transition in reciprocal space. The calculated tunneling and photoemission
spectra are consistent with the phenomenology of the normal state of cuprates.
We derive a low-energy description of these effects using a generalization of
the slave-boson method.
