Signal Monte Carlo

The signal Monte Carlo is based on an updated version (September 3, 1999) of the NUSIM neutrino simulation program written by Gary Hill. The code was improved to increase the efficiency of the neutrino-induced muons that reach the detector. This is described in detail in appendix D. The processing chain and hit cleaning is the same as for background Monte Carlo (appendix A, except NUSIM is used to generate the signal events. The simulation artificially hardens the spectra of signal events to increase the relative number of the highest energy events. A weight is assigned to the events to produce the desired power law energy spectra. Note that in table 1, the number of events that survived the various cuts for the signal MC are not weighted, so the numbers in the table are only representative of the true efficiencies. A more accurate calculation of relative efficiencies with proper weighting is discussed in section 3.2.1. Due to our interest in sources with hard spectra, few events with $E_{\nu}<$1 TeV were expected. Therefore the simulation initially restricted the interval of neutrino energies to 1 to 1000 TeV. Optimization of the analysis procedures were developed by assuming a weighting appropriate for the E^-2<> distribution, yet significant sensitivity was found for softer power laws . We discuss our procedure to weight the effective area calculation in section 4.2.

Lower energy signal Monte Carlo was also generated using an older version of NUSIM (December 3, 1998). The previously mentioned corrections to NUSIM for the high energy signal were not done. Hence $\sim$20% of the neutrino events don't have muons, and thus less statistics for triggered events. None the less, the results from the low energy signal sample is still consistent with the high energy signal sample. The neutrino energy range is 10 GeV to 10^5.5<> GeV. This sample of MC events containing lower energy signal were used to calculate the muon effective areas and flux limits for $E_{\mu}>$10 GeV. This enables us to investigate our sensitivity at lower energies.