First All-Sky Measurement of Muon Flux with IceCube IceCube REU Summer 2008 Kristin Rosenau Advisor: Teresa Montaruli

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.

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

IceCube Neutrino Telescope

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

Reality Ideal Situation (Horizon)

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

Effect of Cuts 1.5º 1º 20º 3º 1º “Good” events “Bad” events where  = efficiency

Determining cut parameters based on optimization Optimization Variable Cut Parameter Sigma Zen<.03 radians Direct Length>200 m Reduced Likelihood<11

Optimization Misreconstructed Muons Reduction in misreconstructed muons (Horizon)

Optimization The ratio of good events to bad events: 70º

Angular Resolution Before cuts After cuts

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.

Single vs. Coincident Muons Coincident Muons compose about 5% of all downgoing muons. Effect from muon filtered data

Single vs. Coincident Muons Coincident Muons dominate below the horizon

Background Suppression Optimization Variable Cut Parameter Sigma Zen<.03 Direct Length>300 m Reduced Likelihood<9 Split Psi<.7 Line Fit Speed>.15 and <.4 Track Smoothness>-.4 and <.4 Direct Hits>7 The following cut parameters were chosen because they eliminated the misreconstructed muons close to and below the horizon.

Background Suppression angular resolution quality parameter before cutsafter cuts

Single vs. Coincident Muons Single and coincident muons have been eliminated past the horizon.

Coincident Muons

Optimization 1: No Cut 2: Minimum Cut 3: σ_zen<3° 4: σ_zen 300m 5: σ_zen 300m and L_red 7 6: σ_zen 300m and L_red 7 and Split_psi 7

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.

IceCube-22 Data Minimum Bias Data  Keeps every 200 th event Muon Filtered Data  Keeps all events below 70º because the neutrinos below the horizon are the focus

IceCube-22 Data The initial cut was applied to the Minimum Bias Data The final cut was applied to the Muon Filtered Data

Results

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 Response of AMANDA-II to Cosmic Ray Muons; Universal Academy Press, Inc

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