Collimation Issues for the Pep-ii B-factory

This note describes how beam collimation affects detector backgrounds at the collision point for the PEP-II Bfactory, a joint effort of three laboratories: LBNL, LLNL, and SLAC. Beam collimation controls the transverse size as well as the maximum allowed energy spread of the beam. The location of synchrotron radiation masks is determined by the transverse size of the beam in that the masks must prevent radiation generated by beam particles located at large transverse beam positions from directly striking the detector beam pipe. Collimation of the energy spread of the beam is important in the control of backgrounds produced by beam particles that strike a gas molecule (lost beam particles). I describe some preliminary information from background studies during the first months of commissioning the high energy ring of the PEP-II B-factory and present some model predictions for synchrotron radiation backgrounds when collimators are not present.