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Systematics
Below is a summary of the systematic uncertainties for this analysis. The total systematic uncertainty is obtained by square-root of sum of squares from each systematic source. Each subsequent section gives the details of the study for every systematic source.
| . | E-2 Signal | Atmospheric | CORSIKA |
| Ice properties | ± 24.9% | ± 17.8% | ± 12.4% |
| DOM efficiency | -0.1% +12.6% | -11.7% +17.2% | n/a |
| Cross-sections | ± 8.7% | ± 8.8% | n/a |
| Seasonal variation | n/a | n/a | ± 0.5% |
| Total | -26.4% +29.2% | -23.0% +26.3% | ± 12.4% |
Table 1: Systematic uncertainties.
Ice properties
Datasets
The AHA ice model is used for all analysis simulation for IC40. Only one CORSIKA dataset exists that uses the SPICE ice model to use for systematic studies for IC40, and one neutrino-generator dataset.
Dataset 3404 (3,000 files) single CORSIKA with SPICE1
Dataset 5044 (1,000 files) E-1 &nue with SPICE1
Result
CORSIKA: After level 4 (no events pass levels 5 or 6):
Standard single unweighted CORSIKA (AHA) datasets have a rate of 0.0162783 Hz (× IC40 livetime = 474,305 events)
Systematics single unweighted CORSIKA (SPICE1) dataset has a rate of 0.0142649 Hz (× IC40 livetime = 415,640 events)
This gives a systematic uncertainty for CORSIKA of (AHA-SPICE1/AHA) ± 12.4%
Signal: After final level:
Standard electron E-2 (AHA) datasets have a rate of 7.79205 × 10-6 Hz (× IC40 livetime = 227.04 events)
Systematics electron E-2 (SPICE1) dataset has a rate of 5.85199 × 10-6 Hz (× IC40 livetime = 170.512 events)
This gives an E-2 systematic uncertainty of (AHA-SPICE1/AHA) ± 24.9%
Standard electron Atmospheric (AHA) datasets have a rate of 6.78785 × 10-8 Hz (× IC40 livetime = 1.9778 events)
Systematics electron Atmospheric (SPICE1) dataset has a rate of 5.58296 × 10-8 Hz (× IC40 livetime = 1.62673 events)
This gives an Atmospheric systematic uncertainty of (AHA-SPICE1/AHA) ± 17.8%
DOM efficiency
Datasets
Unfortunately only muon neutrino E-1 datasets with altered DOM efficiency have been produced for IC40. However, these can still be used to estimate systematics.
Dataset 3264 (1,000 files) DOM efficiency = 90%
Dataset 3265 (1,000 files) DOM efficiency = 110%
Result
After final level:
Standard muon E-2 neutrino signal (DOMeff=100%) datasets have a rate of 2.71289 × 10-6 Hz (× IC40 livetime = 79.0463 events)
Systematics muon E-2 neutrino signal (DOMeff=90%) dataset has a rate of 2.71657 × 10-6 Hz (× IC40 livetime = 79.1536 events)
Systematics muon E-2 neutrino signal (DOMeff=110%) dataset has a rate of 3.05471 × 10-6 Hz (× IC40 livetime = 89.006 events)
This gives a E-2 systematic uncertainty of -0.1% +12.6%
Standard muon Atmospheric neutrino signal (DOMeff=100%) datasets have a rate of 5.59485 × 10-8 Hz (× IC40 livetime = 1.63019 events)
Systematics muon Atmospheric neutrino signal (DOMeff=90%) dataset has a rate of 4.9411 × 10-8 Hz (× IC40 livetime = 1.43971 events)
Systematics muon Atmospheric neutrino signal (DOMeff=110%) dataset has a rate of 6.55868 × 10-8 Hz (× IC40 livetime = 1.91103 events)
This gives a Atmospheric systematic uncertainty of -11.7% +17.2%
Cross-section
Datasets
The cross-section model used for all IC40 neutrino datasets is hteq (except for tau neutrino). A newer cross-section model that is used is the CSS model. An electron neutrino E-1 dataset is used for a systematics study.
Dataset 5102 (500 files) CSS cross-section
Result
After final level:
Standard electron E-2 neutrino signal (hteq) datasets have a rate of 7.79205 × 10-6 Hz (× IC40 livetime = 227.04 events)
Systematics electron E-2 neutrino signal (css) dataset has a rate of 7.11563 × 10-6 Hz (× IC40 livetime = 207.331 events)
This gives a E-2 systematic uncertainty of (css-hteq/hteq) ± 8.7%
Standard electron Atmospheric neutrino signal (hteq) datasets have a rate of 6.78785 × 10-8 Hz (× IC40 livetime = 1.9778 events)
Systematics electron Atmospheric neutrino signal (css) dataset has a rate of 6.19006 × 10-8 Hz (× IC40 livetime = 1.80362 events)
This gives a Atmospheric systematic uncertainty of (css-hteq/hteq) ± 8.8%
Seasonal variation
The CORSIKA is simulated with the assumption of on October atmosphere. This turns out to be very close to the average over the whole year, however it still contributes to a small systematic uncertainty.
Rate for IC40 is 1341.28 Hz
Rate for October is 1347.82 Hz
This gives a systematic uncertainty of (October-Year/Year) ± 0.5%
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