J un 2 00 0 1 Polarized Protons in HERA
Polarized proton beams at HERA can currently only be produced by extracting a beam from a polarized source and then accelerating it in the three synchrotrons at DESY. In this paper, the processes which can depolarize a proton beam in circular accelerators are explained, devices which could avoid this depolarization in the DESY accelerator chain are described, and specific problems which become important at the high energies of HERA are mentioned. At HERA’s high energies, spin motion cannot be accurately described with the isolated resonance model which has been successfully used for lower energy rings. To illustrate the principles of more accurate simulations, the invariant spin field is introduced to describe the equilibrium polarization state of a beam and the changes during acceleration. It will be shown how linearized spin motion leads to a computationally quick approximation for the invariant spin field and how to amend this with more time consuming but accurate non-perturbative computations. Analysis with these techniques has allowed us to establish optimal Siberian Snake schemes for HERA.
Acceleration of polarized protons to 820-GeV at HERA
The SPIN Collaboration and the DESY Polarization Team have studied the possible acceleration of a polarized proton beam to 820 GeV/c in the HERA accelerator complex at DESY. The main problems which need further study are: increasing the accumulated polarized proton intensity, providing adequate spin stability with four or more Siberian snakes in HERA. All other problems appear to have straightforward solutions using existing techniques. The rst Section of this Report summarizes the changes needed in each accelerator for polarized proton acceleration; it also contains a possible Schedule and Budget for the polarized proton beam project. The rest of the Report describes a possible plan to accelerate polarized protons and to perform polarized proton experiments at 820 GeV/c.
Double Scattering of Electrons with Magnetic Interaction
The Mott theory of double scattering of electrons by nuclei is extended to the case where a constant homogeneous magnetic field intervenes between the two scattering centers. The problem is treated in the Foldy-Wouthuysen representation. It is found that the presence of the magnetic field causes the asymmetry in the double-scattering cross section to be altered, and that this change in the asymmetry can be utilized to determine the gyromagnetic ratio of the free electron.