Description
Collisions of heavy ions performed at the Relativistic Heavy Ion
Collider (RHIC) have opened the door to a new understanding of strongly
interacting matter under extreme conditions. Studies of particle
production from interactions of gold nuclei at very high energies have
revealed a state of matter that is opaque to high momentum quarks and
gluons. This widely accepted picture of the matter produced in heavy ion
collisions is dependent upon an understanding of particle production in
smaller systems. To further the understanding of such systems, the
PHOBOS experiment at RHIC measured particle production in deuteron-gold
(d+Au) collisions. Special calorimeter detectors were installed prior to
the d+Au physics run that allowed PHOBOS to measure forward-going
protons, complementing the ZDC detectors that observed forward-going
neutrons. These detectors allowed neutron-gold (n+Au) and proton-gold
(p+Au) interactions to be extracted from the d+Au collision data. The
commissioning and performance of the proton calorimeter detectors will
be discussed. Studies of particle production in d+Au, p+Au and n+Au will
be presented to answer some basic questions about the validity of d+Au
as a reference for Au+Au, about how particle production depends on
system size, and about charge transport in nucleon-nucleus interactions.