The relevance of the magnetic field in the Level-1 trigger

We study the influence of the shape and strength of the magnetic field between the VELO and TT on the performance of the Level-1 trigger. The effects of various fields on the momentum and impact-parameter resolution at the trigger level are investigated with the use of a stand-alone simulation program. The variations in momentum resolution are propagated to the Level-1 trigger decision algorithm, run in the full detector simulation, in order to estimate the overall trigger efficiency as a function of magnetic field strength. The possibility of enhancing the trigger performance by improving the resolution of TT in the inner region is also explored.