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GRB Sensitivity Studies: IC-86 & High Energy Extensions Madison Collaboration Meeting 2009

This study presents sensitivity analyses for GRB samples, rates determined by satellite observations, and event simulations for neutrino spectra. The data is based on a sample from 2007-2009, randomly distributed in detector coordinates with assigned average parameters. The effective area and event rates for IC-86 and proposed high energy extensions are analyzed, along with event selections and event rates for discrete GRBs. The study also explores the discovery potential and suggests future investigations using different geometries and methods.

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GRB Sensitivity Studies: IC-86 & High Energy Extensions Madison Collaboration Meeting 2009

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  1. GRB Sensitivity Studies with IC-86 and proposed High Energy ExtensionsMadison Collaboration Meeting 2009 Erik Strahler UW-Madison 28/4/2009

  2. GRB Sample [procedure] • Rates determined by satellite Observations • ~200 Fermi Bursts / yr. • ~100 Swift-like Bursts / yr. • To preserve correlations between photon parameters, sample entire bursts • Sample from 2007-2009 gives good distribution • Distribute randomly and istotropically in detector coordinates • Assign average parameters to unmeasured quantities • z = 2 • Ebreak = 0.2 MeV • If no spectra measured, a = -1, b = -2 • If only a measured, b = a – 1 (or cutoff, if reported by satellites) • Liso = 1x1051 ergs/s for Swift bursts, 1x1052 erg/s for Fermi bursts

  3. GRB Sample [distributions] Fermi Swift

  4. GRB Sample [results] • Sampled 365 days worth of bursts over the full-sky • 180 Fermi GRBs, 106 Swift GRBs; 142total Northern Sky GRBs • 6839 s prompt window ontime • Calculate neutrino spectra via standard way (Guetta et al.)

  5. Simulation • Default (IC-86) and Extended Geometries • Filtered and preselected by Dima (SBM selection) • Remaining Events • Very poor background statistics • Should be improving in the next weeks

  6. Default (IC-86) Event Selection Cut on SBM parameter to remove all background muons above 85 degrees

  7. IC-86 Effective Area

  8. IC-86 Event Rates [isotropic MC] • Apply SBM quality cut • Weight all-sky simulation to appropriate flux • Gives angle averaged event rates

  9. IC-86 Event Rates [discrete GRBs] • Create point source MC at each GRB location • Take simulated neutrinos in 2.5 degree zenith band around GRB • Rotate MC event coordinates to GRB • Apply 2 degree angular cut around all GRBs • Retains 70-90% of signal depending on declination and spectrum • Not applied to IND spectra numbers (coming soon) • Removes majority of atm. neutrino background • Rescale atm. neutrinos to appropriate on-time

  10. HE-EXT9 Geometry

  11. HE-EXT9 Event Selection Cut on SBM parameter to remove all background muons above 85 degrees

  12. Effective Area Ratio

  13. Ratio of GRB event rates

  14. HE-EXT9 Event Rates [discrete GRBs] • 2 degree angular cut is harsher for the HE event sample • To try: loosen cut till backgrounds are at same level as IC-86 selection

  15. Discovery Potential

  16. To Do • Investigate individually modeled bursts with very high event rates • Apply unbinned likelihood method • Take full advantage of extra events at high energy • Get more background statistics! • Run same checks with 110-string geometry

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