South Pole Ice model

Dmitry Chirkin, UW, Madison

http://icecube.wisc.edu/~dima/work/WISC/ppc/spice/

IceCube in-ice calibration devices

3 Standard candles56880 Flashers7 dust logs

Flasher dataset

Simulation

Fla

sher

405

nm

For

muo

ns:

fold

ed w

ith

Che

renk

ov s

pect

rum

Sample Cherenkov photons from this curve

Angular sensitivity

Fitting the data

1 event simulated

4 events

10 events

Red: AHABlack: SPICE

• 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

Likelihood description of data

Find expectations for data and simulation by minimizing –log of

Regularization terms:

Measured in simulation: s and in data: d; ns and nd: number of simulated and data flasher events

Sum over emitters, receivers, time bins in receiver

Dependence on initial seed

Including the dust logger data

Correlation with dust logger dataef

fect

ive

sca

tter

ing

coef

ficie

nt (from Ryan Bay)

Scaling to the location of hole 50

fitted detector region

Merged data

Refining the solution

Refining the solution

7% in a1% in be

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

History of changes11/19/09 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 17.8 --> 16.51 cm (cosmetic change: modifies only the meaning of py) * fixed the DOM angular sensitivity curve (removed upturn at cos()=-1).

SPICE models

py=3.1

py=2.1

SPICE models

SPICE models

SPICE models

SPICE models vs. AHA

Ratio to SPICE2x

7% uncertainty 5% uncertainty

py=3.1py=2.1

Why does AHA not work?

Fits systematically offPoints at same depth not consistent with each other!

Individually fitted for each pair: best possible fit

Why does AHA not work?

Averaged scattering and absorptionFrom ice paper

Measured properties not consistent with the average!Deconvolving procedure is unaware of this and is using the averages as input

When replaced with the average, the data/simulation agreement will not be as good

SPICE vs. AHA: horizontal flashers

SPICE

AHA

SPICE vs. AHA: 45 degree flashers

SPICE

AHA

Single muons generated with mmc

SPICE

AHA

Muon bundles generated with corsika

SPICE

AHA

Nch of flasher events

Improvement in simulation

by Anne Schukraft by Sean Grullon

Downward-going CORSIKA simulation Up-going muon neutrino simulation

Unfolded data with only events in the top or bottom

preliminary preliminary

IC-22 atmospheric neutrino analysis

IC-22 unfolding result

• 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)

preliminary

Conclusions and outlook

1. 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+)

2. Rapid progress in simulation leads to very good agreement with data: In-situ flasher simulation background muon simulation neutrino simulation

3. Uncertainties on the model are ~ 5% on scattering and ~ 7% absorption Need to understand remaining ~ 7% disagreement between timing

and amplitude distributions

4. Future: measure the wavelength dependence with the standard candle