  To interpret the measurements in heavy-ion collisions at the Relativistic
Heavy-Ion Collider (RHIC) it is crucial to understand the initial state of the
colliding gold (Au) nuclei. The parton distribution in Au nuclei is modified
compared to protons, and their isospin composition is different due to the
presence of neutrons. d+Au collisions at RHIC at the same collision energies
are an important tool to study initial state modifications. PHENIX has measured
pi0, eta, and reconstructed jets at high transverse momentum. These data are
compared to predictions from nuclear parton distribution functions.
Furthermore, single electrons from heavy-flavor decays have been measured by
PHENIX.
