Experiments on beam-beam depolarization at LEP

The possibility of obtaining transverse polarization with colliding beams was studied at LEP during 1994. A level of transverse beam polarization of 40% was achieved with e⁺e^- collisions in one of the experimental interaction points. The collision of one electron and one positron bunch was 1.5×10³⁰ cm ^-2 s^-1. The polarization level was not limited by the beam-beam interaction: from three circulating electron bunches only one was colliding with one positron bunch, whereas the beams were separated by electrostatic deflectors at the interaction points of the other electron bunches. No significant difference between the polarization level of colliding and non colliding bunches was noticed. Betatron- and synchrotron frequencies as well as spin tune were chosen in order to avoid beam-beam driven depolarizing resonances