The PHENIX vertex detector upgrade

The PHENIX experiment at the Relativistic Heavy Ion Collider studies strongly interacting matter in nucleus-nucleus, polarized proton-proton and proton (deuterium)-nucleus collisions. Its prime fields of research are the exploration of hot and dense nuclear matter, studies of the gluon spin composition of the nucleon, and investigations of parton structures in nuclei. The experiment is being upgraded with a silicon vertex detector that will substantially enhance the physics capabilities of its central arm spectrometers. The silicon vertex detector consists of a four-layer barrel, built from two internal layers of pixel detectors and two external layers of projective "strip-pixel" detectors which complement the central electron spectrometer arms of PHENIX. In this paper, the physics motivation of the upgrade and the concept of the new detector are outlined. The status of new developments and the beginning production of the silicon detectors are presented.