In order to measure the mass of the eta meson with high accuracy using the d+p -> 3He+eta reaction, the momentum of the circulating deuteron beam in the Cooler Synchrotron COSY of the Forschungszentrum Juelich has to be determined with unprecedented precision. This has been achieved by studying the spin dynamics of the polarized deuteron beam. By depolarizing the beam through the use of an artificially induced spin resonance, it was possible to evaluate its momentum p with a precision of dp/p < 10-4 for a momentum of roughly 3 GeV/c. Different possible sources of error in the application of the spin resonance method are discussed in detail and its possible use during a standard experiment is considered.
@article{arxiv.0908.3103,
title = {High precision beam momentum determination in a synchrotron using a spin resonance method},
author = {P. Goslawski and A. Khoukaz and R. Gebel and M. Hartmann and A. Kacharava and A. Lehrach and B. Lorentz and R. Maier and M. Mielke and M. Papenbrock and D. Prasuhn and R. Stassen and H. J. Stein and H. Stockhorst and H. Ströher and C. Wilkin},
journal= {arXiv preprint arXiv:0908.3103},
year = {2010}
}