  The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory
has been in operation since 2000. Over the past decade, the luminosity in the
polarized proton (p-p) operations has increased by more than one order of
magnitude. The maximum total beam-beam tune shift with two collisions has
reached 0.018. The beam-beam interaction leads to large tune spread, emittance
growth, and short beam and luminosity lifetimes. In this article, we review the
beam-beam observations during the previous RHIC p-p runs. The mechanism for
particle loss is presented. The intra-beam scattering (IBS) contributions to
emittance and bunch length growths are calculated and compared with the
measurements. Finally, we will discuss current limits in the RHIC p-p
operations and their solutions.
