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

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

GRB Sample [distributions] Fermi Swift

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

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 Geometry Neutrinos Corsika Coincident IC-86 7292 7 4 HE-EXT9 7361 6

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

IC-86 Effective Area

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

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 Emission Phase Signal Events Signal Fraction Background Events Prompt (WB) 6.17 78% 0.006 Prompt (IND) 18.9 (2.6 with all Liso=1x1051 ergs/s) Precursor 5.2 69% 0.015

HE-EXT9 Geometry

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

Effective Area Ratio

Ratio of GRB event rates

HE-EXT9 Event Rates [discrete GRBs] Emission Phase Signal Events Signal Fraction Background Events Prompt (WB) 6.22 75% 0.0047 Prompt (IND) 20.3 (angular cut not applied) Precursor 5.16 65% 0.009 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

Discovery Potential

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