The results presented in the following sections were obtained using version 2.3 of the simulation code PISA. A special event generator was created which emitted either muons or pions at fixed momenta from the vertex of the PHENIX detector system. Runs were made for launch momenta of 1.5, 1.7, 2.25, 3.0, 5.0, and 8.0 GeV/c.
The azimuthal angle was selected at random from 0 to 360 degrees and the polar angle ranged from 10 to 30 degrees. These angular ranges resulted in hits distributed uniformly over the front face of the muon magnet yoke with all particle trajectories having initial momenta greater than 1.7 GeV/c penetrating the full six layers of the muon identifier.
For each initial momentum 2000 muon ``training'' events and 2000 ``test'' events were run for a total of 4000 particles. For pions, at momenta below 5.0 GeV/c, so few particles produced hits in the muon identifier that more than 4000 particles were launched in order to obtain at least 2000 roads in the muon identifier. For the 3.0 GeV/c case, a total of 8000 pions were launched and for momenta lower than this, 16,000 pions were launched.
Most of the material through which the particles must penetrate to reach the muon identifier was omitted from the simulations. In particular, the central magnet, lead shield, and neutron shield were omitted. The tracking chambers, however, were not removed because hits recorded in station three were used in the analysis program PISORP to discard pion events in which the primary particle decayed to a muon.
In the sections which follow, the particle momenta quoted are the primary momenta at the vertex. Since almost all material between the vertex and the muon identifier was removed from the muon arm, the momentum of a particle incident on the front face of the muon magnet yoke is essentially the same as the momentum at the vertex. If all materials were installed, including the lead shield and the neutron shield, the corresponding vertex momentum would have to be increased by approximately 1.3 GeV/c for comparison with the results shown in the following sections.