Calculating the polarization lifetime from the Thomas-Bargmann-Michel-Telegdi equation

It was observed at the Relativistic Heavy Ion Collider that the polarization of the stored beam decays by 0.17 to 3% per hour. This effect could not be simulated up to now since the simulation time for an exact calculation exceeded the computer capacity. To solve this problem the action of the whole arc was considered as one element acting on the spin and not, as before, each optical element in the arc individually (called lattice independent integration). In addition to former simulations the coupling of synchrotron and betatron motions in the beam interaction regions and their action on the polarization were taken into account (called addition of longitudinal dynamics). It is shown that with these two changes the action on the polarization life time can be explained.