| Popis: |
The observed cutoff in the cosmic ray spectrum leads to a highly motivated expectation of an ultra-high energy (UHE) neutrino flux, coming from interactions between the cosmic rays and cosmic microwave background photons. Although no UHE neutrinos have yet been detected; better background separation and removal will help accelerate the search.Past flights of the ANtarctic Impulsive Transient Antenna (ANITA) experiment have set the strongest limits on the UHE neutrino flux above 10^{19} eV. Due to the advanced sensitivity of future flights to both signal and anthropogenic backgrounds, the techniques used in the past analyses may not be sufficient to remove backgrounds. Here, we discuss processes developed for this analysis. First, we discuss newly techniques to filter event waveforms in both the amplitude and phase spectra. These new techniques were applied to the ANITA-2 experiment data set. We discuss a new technique developed that uses equal area bins of ice on the Antarctic continent. Further, we define a set of analysis cuts, how the analysis cuts were optimized for maximum sensitivity for UHE neutrinos, how the number of background and neutrino events were estimated. For our search, we used the maximal Kotera et. al. 2010 flux model and optimized based on this model. After optimization, we found zero events from the 10% sample passing all cuts.These techniques will prove useful for future flights of ANITA as the sensitivity of the instrument increases. The optimization procedure can also provide a starting point for future analysis. The filtering technique shown here decreased mis-reconstruction in pointing of events. The HealPix method, while requiring further refinement, shows promise by retaining valuable areas of ice that may have been removed from previous analyses. |
