GEANT simulations of the spectrometer design are in progress. They are addressing the following questions:
Figures 1 and 2 show GEANT calculations of passage of muons through different materials. The advantage of the Al2O3 versus Al as a stopping material is clearly seen in reduction of moun range in Al2O3 by ~ 50% without a significant increase of the multiple scattering angle.
The importance of muon multiple scattering in the filter is demonstrated in figure 3. It shows correlations between the radial distances R (in cm) from the beam axis of positive and negative muons resulting from the decay of 30 GeV J/Psi beam, at the location of a hodoscope placed 4 m away from the target, without and with the hadron filter (in these calculations, to preserve the radial symmetry, the magnetic field was turned off). The Al2O3 filter, 2 m long, is positioned directly behind the target.