1. IceCube Collaboration Meeting Ghent, October 9, 2007
Optical Properties of Ice and Our Modeling Thereof Kurt Woschnagg 1. Imperfections in the millennium ice model 2. The new ice model: AHA 3. Selected simulation results with AHA
IceCube Collaboration Meeting
Ghent, October 9, 2007

2. The millennium model Scattering Absorption Main uncertainties:
► measurements done horizontally → “smearing” of layer structure
► dearth of data below 2100 m → deep extrapolation with ice core data

3. Is a detailed model needed?
Light flux from a muon in…
…”bulk” ice …millennium ice

4. Is a detailed model needed?
[Oxana Tarasova]
AMANDA cascades (L2)
PTD/MAMINT
photonics/millennium

5. Unresolved systematics in the millennium model
The Stephan plot
Relative OM “sensitivities” by
S. Hundertmark et al.
millennium ice
photonics
AMASIM B C A
depth
1900
1800
1700
1600
1500

6. Photonics Full Circle Test
message:
layer
smearing
observed
stronger for
absorption

7. Extending the Ice Map for IceCube
Need to complement AMANDA data

8. Evidence for clean deep ice: flasher data
PRELIMINARY

9. Evidence for clean deep ice: IC9 data/MC
[Jon Dumm]
Ratio of Exp / Sim
Structure washed out in MC
Not enough light near bottom in MC

10. Evidence for clean deep ice: IceTop/InIce coinc.
[Tom Gaisser]
~0.5 EeV
~2000µ
Known
muon flux
muon “visibility radius”
propagation
length (y2k)

11. Added full millennium ice layering
The ice properties were measured with a homogeneous photon simulation.
Added full millennium ice layering

12. Look at photons recorded at same depth as source…
…where they spent their time:
…what kind of ice they saw:

13. Smearing depends on source…
532 nm
470 nm
337 nm

14. Averaging over
wavelength and
distance

15. Wavelength/distance averaged layer smearing

16. Distinguishing scattering from absorption
“Lundberg epiphany”
Scattering regime
Absorption regime
inexact regime definition (→ knob to turn), but simple and fast

17. Ice model tweaking: layer unsmearing
Final stretching
stretch and repeat

18. Ice model tweaking: new extrapolation to deep ice
Extrapolation was based on Vostok+Dome Fuji ice cores
Deep ice too clean to use Dust Logger data
Newer and better ice core data from EDML:

19. Ice model tweaking: new extrapolation to deep ice

20. The Additionally Heterogeneous Absorption model
Amplitude-
stretched
Cleaner

21. The Additionally Heterogeneous Absorption model
Main Uncertainties:
Scattering/absorption regimes defined too crudely
May have resulted in overstretching of absorption
If modification needed: make more sophisticated analysis
Deep ice may need update
Complete analysis of bulk ice flasher data
Compare with flasher simulations (need tables)
Compare with Albrecht’s flasher calibration…

22. Photonics full circle test with AHA
Near…

23. Photonics full circle test with AHA
Far…

24. Photonics full circle test with AHA
Averaged over
typical
measurement
distances

25. Simulations with AHA: did it help?
[Oxana Tarasova]
AMANDA cascades: background
zreco
Photonics tables: 20 m binning in source depth

26. Simulations with AHA: did it help?
[Oxana Tarasova]
AMANDA cascades: signal
zreco
Photonics tables: 20 m binning in source depth

27. Simulations with AHA: did it help?
[Jon Dumm]
SPE occupancy (IC22)
Photonics tables: 40 m binning in source depth

28. Simulations with AHA: did it help?
[Peter Niessen]
Photonics tables: 80 m binning in source depth

29. Conclusions: Aha Akbar!
AHA has improved MC/data agreement
→ Systematic uncertainty has been retired
► AMANDA simulation
AHA seems to produce the expected effects
Some indication that layer stretching was overdone
More basic checks needed: Stephan plot, residual times, …
► IceCube simulation
Effects weaker than expected
Not obvious what is going on
Try finer binning in photonics tables
Compare simulations with one thing changing at a time (ice model, DOM efficiencies, simulation version, …)