Polarized Proton Collisions at RHIC

The Relativistic Heavy Ion Collider (RHIC) provides not only collisions of ions but also collisions of polarized pro-tons. In a circular accelerator, the polarization of polarized proton beam can be partially or fully lost when a spin de-polarizing resonance is encountered. To preserve the beam polarization during acceleration, two full Siberian snakes were employed in RHIC. In 2002, polarized proton beams were firs accelerated to 100 GeV and collided in RHIC. Beams were brought into collisions with longitudinal po-larization at the experiments STAR and PHENIX by us-ing spin rotators. Optimizing polarization transmission ef-ficien y and improving luminosity performance are signifi cant challenges. Currently, the luminosity lifetime in RHIC is limited by the beam-beam effect. The current state of RHIC polarized proton program, including its dedicated physics run in 2005 and efforts to optimize luminosity pro-duction in beam-beam limited conditions are reported