Expected Polarization in the Present PEP - 2 Desi

In the present design of PEP-2, operation with polarized beams is not anticipated. The amount of polarization that the existing design does support is however of interest. Calcdations are presented for the expected polarization for both the High Energy (HER) and the Low Energy (LER) Rings of PEP-2 arising from the Sokolov-Ternov build-up. In both rings, we find that with the detector solenoid turned on, the equilibruim polarization is less than 1% at the design operating energies. Furthermore, if a polmized beam were injwted, it would depolarize in a short time. To improve the polarization, we consider spin matting; i.e., implementing a set of spin transpmency renditions on the lattice design. While to demand mmplete spin trmparency around the entire mane is impractical, six conditions are derived to make the lattice partially spin transparent. Among these six conditions, perhaps only two are dominant for PEP-2. It remains to be seen whether these six (or two) renditions can be implemented into the lattice design in prwtiw, and if implemented, whether they are sufficient to increase the polarization to usefti levels. We have not studied spin rotator s~emes to provide longitudinal polarization at the interaction point or their effect on the beam polarization. Similar calculations are presented for the Beijing Tau-Charm F~tory (BTCF) dmign, including a possible spin rotator scheme. It is found that when this spin rotator is turned on without spin matching, the polarization leyel is low. 1 Polarization of the Present PEP-2 Design The s&ematics layouts of the PEP-2 high and low energy rings as well as of the BTCF are shown in Fig. 1. The PEP-2 lattices [1] have been designed tting into account important constraints (tunnel size restrictions, for example), but have not been optimized for maintaining beam polarization. Specifimlly, the design includes solenoids, skew quadruples, and vertical bending magnets. Past experience has shown such elements to be potentially strong