First AllSky Measurement of Muon Flux with IceCube

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First All-Sky Measurement of Muon Flux with
IceCube

• IceCube REU Summer 2008
• Kristin Rosenau
• Advisor Teresa Montaruli

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IceCube Neutrino Telescope

• Located at the geographic South Pole
• Buried beneath roughly 1.5 km of ice, extending
  down to 2.5 km.
• Antarctic Muon and Neutrino Detector Array
  (AMANDA) was the proof of concept for IceCube
• 4,800 Digital Optical Modules (DOMs), or
  photomultiplier tubes, are inserted into the ice
  on 80 cables referred to as "strings."
• Each string holds 60 DOMs.

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IceCube Neutrino Telescope

• Works on the principle of Cherenkov Light
• Muons produced by cosmic rays in the atmosphere
  are background for astrophysical searches
• Neutrinos cannot be detected directly
• Neutrinos convert into muons inside the Earth
• Earth is used as a filter against background

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IceCube Neutrino Telescope
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Project Objective

• Goal The first all-sky measurement of muon flux
  with IceCube.
• Muons are a calibration tool for IceCube.
• Unprecedented statistics for these events
• Project Steps
• Initial Cuts (weak)
• Final Cuts (hard)
• Compare IceCube-22 (IC-22) data with Monte Carlo
  simulation

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Ideal Situation
(Horizon)
(Horizon)

• Reality

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Useful Variables

• Variables with highest degrees of correlation to
  the angular resolution (which indicate a quality
  parameter)
• Sigma Paraboloid
• Direct Length
• Reduced Likelihood

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Effect of Cuts
where ?efficiency
1.5º
1º
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Determining cut parameters based on optimization

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Optimization
Misreconstructed Muons
(Horizon)
Reduction in misreconstructed muons
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Optimization

• The ratio of good events to bad events

70º
70º
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Angular Resolution
Before cuts
After cuts
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Coincident Muons
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Coincident Muons

• The Monte Carlo coincident muon data only saves
  the data for one track
• Case 1
• The reconstructed track belongs to the correct
  true track.
• Minimum Zenith Angle Error
• Case 2
• The reconstructed track belongs to the wrong true
  track.
• Maximum Zenith Angle Error
• Case 3
• The muon is misreconstructed.

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Single vs. Coincident Muons
Effect from muon filtered data

• Coincident Muons compose about 5 of all
  downgoing muons.

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Single vs. Coincident Muons
Coincident Muons dominate below the horizon
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Background Suppression

• The following cut parameters were chosen because
  they eliminated the misreconstructed muons close
  to and below the horizon.

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Background Suppression
quality parameter
before cuts
after cuts
angular resolution
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Single vs. Coincident Muons
Single and coincident muons have been eliminated
past the horizon.
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Coincident Muons
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Optimization

• 1 No Cut
• 2 Minimum Cut
• 3 s_zenlt3
• 4 s_zenlt3 and L_dirgt300m
• 5 s_zenlt3 and L_dirgt300m and L_redlt9 and
  N_hitgt7
• 6 s_zenlt3 and L_dirgt300m and L_redlt9 and
  N_dirgt7 and Split_psilt.7 and .15lt Line Fit Speed
  lt.4 and -.4lt Smoothness lt.4 and N_hitgt7

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Quality Cuts Conclusion

• The initial cuts improved the angular resolution
  of the detector while keeping a significant
  number of the events.
• Although the final cuts were optimized at 3-4,
  the less optimal cuts at 6 were chosen because
  they eliminated all of the misreconstructed muons.

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IceCube-22 Data

• Minimum Bias Data
• Keeps every 200th event
• Muon Filtered Data
• Keeps all events below 70º because the neutrinos
  below the horizon are the focus

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IceCube-22 Data

• The initial cut was applied to the Minimum Bias
  Data

• The final cut was applied to the Muon Filtered
  Data

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Results
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Results
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In the Future

• The muon flux can be used to compare and contrast
  IceCube with other detectors
• It will be used extensively in calibration of the
  IceCube detector

Desiati P. et al. 2003. Response of AMANDA-II to
Cosmic Ray Muons Universal Academy Press, Inc.
1373-1376
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Acknowledgements

• A special thanks to the following people for all
  the advice and help with this project
• Patrick Berghaus
• Teresa Montaruli
• Paolo Desiati
• Albrecht Karle
• IceCube Collaboration
• UW-Madison Astrophysics REU Program
• NSF