1. 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

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

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
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

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]
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

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