Spin dynamics in LEP with 40-100 GeV beams

Radiative spin polarization has been studied in the Large Electron- Positron Collider (LEP) at CERN for beam energies from 40 GeV to 100 GeV. The data cover a unique range of spin dynamics, not previously accessible with other storage rings. After optimization of machine parameters and the successful application of new harmonic spin matching techniques, a transverse beam polarization of 57% was obtained at 44.7 GeV. At 60.6 GeV the maximum level reached 8%. The observed energy dependence of radiative spin polarization at LEP is in excellent agreement with the theoretically expected behavior. The LEP data provide the first experimental confirmation for a theory of depolarization at very high energies, first developed in the 1970s by Derbenev and Kontratenko. The results will help to guide the design of any future high energy electron-position storage ring requiring polarized beams. (13 refs).