1. South Pole Ice model
Dmitry Chirkin, UW, Madison

2. IceCube in-ice calibration devices
3 Standard candles
56880 Flashers
7 dust logs

3. Flasher dataset

4. For muons: folded with Cherenkov spectrum
Simulation
For muons: folded with Cherenkov spectrum
Flasher 405 nm
Sample Cherenkov photons from this curve
Angular sensitivity

5. Fitting the data 10 events 4 events 1 event simulated
Absolute calibration of average flasher is obtained “for free”
no need to know absolute flasher light output beforehand
no need to know absolute DOM sensitivity
2.1
3.1
Red: AHA
Black: SPICE

6. Likelihood description of data
Sum over emitters, receivers, time bins in receiver
Find expectations for data and simulation by minimizing –log of
Measured in simulation: s and in data: d; ns and nd: number of simulated and data flasher events
Regularization terms:

7. Dependence on initial seed

8. Including the dust logger data

9. Correlation with dust logger data
(from Ryan Bay)
effective scattering coefficient
Scaling to the location of hole 50
fitted detector region

10. Merged data

11. Refining the solution

12. Refining the solution
7% in a
1% in be

13. Possible reasons for this discrepancy
flasher directionality was ignored: cylindrical symmetry of the 6-flasher emission pattern was assumed
 checked: simulating flashers with measured directions (6-prong star pattern) reproduces the above result exactly
effects of the hole ice on photon propagation were taken only through the angular sensitivity curve
 however: resulting ice properties are the same (within uncertainties) for either nominal or hole ice angular sensitivity
various issues in recorded waveforms: effects of saturation and undershoot, miscalibration, etc.
 already: using the saturation correction.
Fine structure of ice layers matters?  under investigation

14. History of changes
11/19/09 SPICE (also known as SPICE1): first version
* seeded with AHA as initial solution
* AHA is used for extrapolation above and below the detector
* relies on AHA for correlation relation between be(400) and adust(400).
02/01/10 SPICE2:
* fixed the hdh bug (see ppc readme file)
* seeded with bulk ice as initial solution
* dust logger and EDML data is used for extrapolation
* dust logger data is used to extend in x and y, taking into account layer tilt.
02/17/10 SPICE2+:
* fixed the "x*y" option hit counting in ppc
* be(400) vs. adust(400) relation is determined with a global fit to arrival time distributions.
04/28/10 SPICE2x (this page):
* improved charge extraction in data:
improved merging of the FADC and ATWD charges
implemented saturation correction
fixed the alternating ATWD bug
* updated DOM radius > cm (cosmetic change: modifies only the meaning of py)
* fixed the DOM angular sensitivity curve (removed upturn at cos(q)=-1).

15. SPICE models
py=3.1
py=2.1

16. SPICE models

17. SPICE models

18. SPICE models

19. SPICE models vs. AHA

20. Ratio to SPICE2x
7% uncertainty
5% uncertainty
py=2.1
py=3.1

21. Why does AHA not work?
Individually fitted for each pair: best possible fit
Points at same depth not consistent with each other!
Fits systematically off

22. Measured properties not consistent with the average!
Why does AHA not work?
When replaced with the average, the data/simulation agreement will not be as good
From ice paper
Averaged scattering and absorption
Measured properties not consistent with the average!
Deconvolving procedure is unaware of this and is using the averages as input

23. SPICE vs. AHA: horizontal flashers

24. SPICE vs. AHA: 45 degree flashers

25. Single muons generated with mmc
SPICE
AHA

26. Muon bundles generated with corsika
SPICE
AHA

27. Nch of flasher events

28. Improvement in simulation
by Anne Schukraft
by Sean Grullon
Downward-going CORSIKA simulation
Up-going muon neutrino simulation

29. Unfolded data with only events in the top or bottom
preliminary
preliminary
IC-22 atmospheric neutrino analysis

30. IC-22 unfolding result
preliminary
Despite problems in detector simulation, agreement with Bartol muon neutrino flux was demonstrated
It was decided that the simulation, namely simulation of the ice, needed improvement before this analysis can proceed to claiming a measurement of the neutrino flux.
This problem has been solved!
 redo the analysis (with IC-40)

31. Conclusions and outlook
SPICE (South Pole ICE) model:
fitted to IceCube flasher data collected on string 63
demonstrated remarkable correlation with the dust logger data
therefore was extended to incorporate these data (SPICE2)
uses flasher timing information (since SPICE2+)
Rapid progress in simulation leads to very good agreement with data:
In-situ flasher simulation
background muon simulation
neutrino simulation
Uncertainties on the model are ~ 5% on scattering and ~ 7% absorption
 Need to understand remaining ~ 7% disagreement between timing and amplitude distributions
Future: measure the wavelength dependence with the standard candle