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Erik Strahler University of Wisconsin-Madison For the IceCube Collaboration 2/17/2009

Recent Results of Point Source Searches with the IceCube Neutrino Telescope Lake Louise Winter Institute 2009. Erik Strahler University of Wisconsin-Madison For the IceCube Collaboration 2/17/2009. Outline. Motivation Astrophysical Neutrinos Detection Steady Sources Transients Outlook.

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Erik Strahler University of Wisconsin-Madison For the IceCube Collaboration 2/17/2009

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  1. Recent Results of Point Source Searches with the IceCube Neutrino TelescopeLake Louise Winter Institute 2009 Erik Strahler University of Wisconsin-Madison For the IceCube Collaboration 2/17/2009

  2. Outline • Motivation • Astrophysical Neutrinos • Detection • Steady Sources • Transients • Outlook

  3. Why look for Neutrinos? Neutrinos from GRBs

  4. The Cosmic Ray Connection

  5. Astrophysical Neutrinos • Assume hadronic acceleration with equal energy injection as electrons • Protons interact with Syncrotron and IC photons • Typical energy spectrum: E-2

  6. Neutrino Detection in IceCube -Cherenkov radiation emitted by muon -Optical sensors record arrival time of photons for track reconstruction

  7. dfasdfsadf Detector IceTop • 19 strings • 677 optical modules • Operated 2000-2007 • Now integrated with IceCube 59

  8. Reconstruction • Tracks / Cascades reconstructed based on Cherenkov photon arrival times and intensities. Better Pointing Resolution Better Energy Resolution Better Background Rejection

  9. IceCube Analyses • Cosmic Ray Composition • Supernovae Neutrinos • Atmospheric Neutrinos • Indirect Dark Matter Searches • Diffuse Astrophysical Neutrinos • GZK Neutrinos • Time Integrated Point Sources • Transient Point Sources

  10. Downgoing Muons Signal Neutrinos Atmospheric Neutrinos Atmospheric Neutrinos Signal Neutrinos Downgoing Muons Detection Challenges • Down-going muons from CR showers misreconstructed as up-going • Particularly coincident muons from independent showers • Must reject with tight quality cuts • Up-going atmospheric neutrinos from CR showers on other side of Earth • Softer energy spectrum than signal • Isotropically distributed

  11. Shadow of the Moon • Important verification of timing and angular reconstruction • Structure can reveal anisotropies in resolution

  12. Likelihood Method Partial PDF: Likelihood function: Null hypothesis: Likelihood Ratio: Background PDF from data Maximize LLH ratio by varying ns

  13. Point Source Sensitivity

  14. Point Source Results preliminary • Hottest spot found at r.a. 153º , dec. 11º • est. nSrcEvents = 7.7 est. gamma = 1.65 • est. pre-trial p-value: -log10(p): 6.14 (4.8 sigma) • Post-trials p-value of analysis is ~ 1.34% (2.2 sigma) ...

  15. Fraction of Experiments Multiples of Predicted Flux GRB Search Use measured quantities of all GRBs to model the neutrino emission Discovery Potential: 2.6 * Prediction

  16. GRB Result Value of the likelihood ratio test is consistant with the null hypothesis Preliminary Limit: 4.6 * Predicted Flux Measured

  17. UHE Point Source Sensitivity

  18. UHE Point Source Results • Coordinates: Dec. 1.00°, RA 103.5° (6.9 h) • Bin content: 8 events for 1.19 expected (109 in dec. band) • P-value: 2.9*10-5 (pre-trial prob.), 0.345 post trial • equivalent sigma: 4.02316 (pre-trial), insignificant post-trial preliminary

  19. Conclusions and Outlook • No astrophysical neutrinos yet, but sensitivities improving rapidly • 40 string IceCube configuration online from April 2008 • Already as large as full detector on long axis • Data run complete in April 2009 • 19 additional strings deployed this season. • Fermi Satellite adds significant observation opportunities for GRBs • 80 string IceCube only a few years away. Expect factor 6-10 increase in sensitivity • Hopefully see signal neutrinos very soon!

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