  The PHOBOS experiment at the Relativistic Heavy Ion Collider (RHIC) at
Brookhaven National Laboratory is studying interactions of heavy nuclei at the
largest energies available in the laboratory. The high multiplicity of
particles created in heavy ion collisions makes precise vertex reconstruction
possible using information from a spectrometer and a specialized vertex
detector with relatively small acceptances. For lower multiplicity events, a
large acceptance, single layer multiplicity detector is used and special
algorithms are developed to reconstruct the vertex, resulting in high
efficiency at the expense of poorer resolution. The algorithms used in the
PHOBOS experiment and their performance are presented.
