Flux limits

    

Figure 27: (top left) Neutrino flux limit (90% CL) versus declination averaged over right ascension. Applies for neutrinos energies above 1 TeV. (top right) Muon flux limit (90% CL) versus declination averaged over right ascension. Applies for neutrinos energies above 1 TeV.
Figure 28: (bottom left) Neutrino flux limit (90% CL) versus declination averaged over right ascension. Applies for neutrinos energies above 10 GeV (bottom right). Muon flux limit (90% CL) versus declination averaged over right ascension. Applies for neutrinos energies above 10 GeV.

The muon and neutrino flux limits versus declination are shown in figure 27 for various energy spectra. These limits apply for muon and neutrino energies ><> 1 TeV while figure 28 gives the same information for energies above 10 GeV. Figure 26 illustrates the improvement in the flux limits compared to the results presented by John Kim at the ICRC [7]. The flux limit is a factor of 3 less in vertical direction and approximately a factor of 9 times lower in the horizontal direction.

The improvement is attributed to several factors, primarily due to using the LBNL filter and doubling the live-time. The main factor is using the LBNL filter instead of the Swedish filter. The passing rate relative to triggered events of the E^-2<> signal with the Swedish filter was about 43%, while for the LBNL filter is about 53% (25% increase). Comparisons between the two filters show the signal to noise at zenith angles near the horizon are significantly improved with the LBNL filter over. These results are preliminary. New cut variables will be investigated using the cascade and iterative reconstruction. Further improvements in cut optimization is expected to improve the signal to noise by $\sim$ 50% over a large range of zenith angles.