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Overview

Overview. The IceCube neutrino observatory The GZK mechanism & sources of Extremely High Energy (EHE) neutrinos EHE event topology Reconstructing EHE Events Initial 9 & 80 string GZK analysis Conclusion and future plans. IceTop. IceTop. AMANDA. The IceCube Neutrino Observatory.

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Overview

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  1. Aspen Cosmic Ray Workshop April 18th 2007

  2. Overview • The IceCube neutrino observatory • The GZK mechanism & sources of Extremely High Energy (EHE) neutrinos • EHE event topology • Reconstructing EHE Events • Initial 9 & 80 string GZK analysis • Conclusion and future plans Sean Grullon

  3. IceTop IceTop AMANDA The IceCube Neutrino Observatory • 70-80 Strings (60 DOMs each) by 2011 • 1km3 instrumental volume • Designed to detect neutrino energies from 10MeV (SN) to 100EeV (GZK, TD) Sean Grullon

  4. 2.725 K 411 photons / cm3 π ν ＋ ＋ γ μ ＋ ν e p γ p n E = 100 EeV E’=.3E The GZK Mechanism Sean Grullon

  5. Where Do Astrophysical EHE Neutrinos Come From? GZK(hard, high Emax) - Kalashev et al 2002 GZK (strong evolution) - ibid GZK (standard) - Yoshida Teshima 1993 TD - Sigl et al 1999 Zburst – Yoshida et al 1998 Sean Grullon

  6. t t nt EHE Neutrinos Traveling Through the Earth EHE neutrino mean free path very short! ln ~ 100 km << REarth sccnN ~ 10-6~-4 mb Down-going particles CR m EHE n m m,t • EHE neutrinos mainly horizontal and downgoing. • Atmospheric Muons our main background. m nt m North nm > PeV nm < 1PeV

  7. GZK event rates at IceCube depth Yoshida et. al. (1997) ApJ 479:547 (m=4,Zmax=4)) Function of Zenith Angle Function of Energy • Atmospheric Muons, our main background! Many uncertainties in the spectrum in this energy range. • Uncertainties from Charm contribution and muon bundles Sean Grullon

  8. m p e+e- photo-nuclear g pair-creation bremsstrahlung What do EHE Muons look like? • Significant Energy Losses: dE/dX~bE • Stochastic cascades dominates the “bare muon” cherenkov cone, forming approximately a continuous cylinder of light. • Reliable geometry and energy reconstruction needed! Sean Grullon

  9. Sample EHE Muon: 9EeV 9 EeV ~3000 out of 4800 OMs hit! Sean Grullon

  10. Sample Bright Events from 9-String data Sean Grullon

  11. Sample Bright Events from 9-String data Sean Grullon

  12. Waveforms from EHE Muons • EHE muons produce wide, complex waveforms • Width scales with distance (diffusion over large distances) • Total amplitude of waveform (in photoelectrons) scales with muon energy. • Use waveform information for event reconstruction! [mV] [nsec] [mV] [nsec]

  13. Waveform-based Reconstruction • Waveforms have a lot of information; use them in a Maximum Likelihood Technique to reconstruct the particle. • Given a particle (the “hypothesis”) what is the probability of observing a given waveform f(t)? Product of Poisson probabilities over waveform bins: Observed Waveform “Expected” Waveform time Sean Grullon

  14. Initial GZK Analysis • Waveform-based reconstruction algorithm still under development. • Initial GZK analysis performed with simple variables only, observed NPE and “first guess” zenith information. (A. Ishihara astro-ph/0611794) • Yoshida-Teshima GZK flux used (S. Yoshida et. al. (1997) ApJ 479:547 (m=4, Zmax=4)) • Analysis done with 9 string and 80 string configuration Sean Grullon

  15. NPE-Energy Correlation: 9-String MC m t Log10(NPE) Log10(Energy) (GeV) A. Ishihara astro-ph/0611794 Sean Grullon

  16. 9-string NPE distribution from Data Cos (zenith) Log10(NPE) Log10(NPE) Sean Grullon

  17. Event Selection – 9 String MC GZK m Atm m Keep GZK t Cos(zenith) Log10(NPE) Sean Grullon

  18. IceCube Preliminary GZK m0.067 events/year GZK t0.055 events/year Atmospheric m0.009 events/year GZK: S. Yoshida et. al. (1997) ApJ 479:547 (m=4, Zmax=4) Preliminary Event Rate: 9 String Configuration Atmospheric m GZK m GZK t Sean Grullon

  19. Preliminary IceCube 9 String Sensitivity GZK (Strong Ev.) GZK (Standard) Sean Grullon

  20. IceCube Preliminary GZK m0.35 events/year GZK t0.31 events/year Atmospheric m0.033 events/year GZK: S. Yoshida et. al. (1997) ApJ 479:547 (m=4, Zmax=4) Preliminary Event Rate: 80 String Configuration Using MC Zenith GZK m GZK t Atmospheric m Event Rate [/year] Event Rate [/year] A. Ishihara astro-ph/0611794

  21. IceCube 80 String Sensitivity 5 year run looking for events with energy deposit DE > 10PeV Detector Response *NOT* Yet Taken Into account. S. Yoshida et. al. (2004) Phys. Rev. D 69 103004 Sean Grullon

  22. Summary and Outlook • We have now deployed 22 strings providing ~ 25% of the full IceCube volume • GZK analysis efforts underway! Final 9-string results to be published in ICRC2007 • Reliable reconstruction needed; waveform based reconstruction needs to be finalized and tuned. • Apply the waveform based reconstruction to the already ongoing GZK analysis. • Uncertainties in the atmospheric muon background need to be understood. Sean Grullon

  23. Backup Slides! Sean Grullon

  24. Yoshida-Teshima vs. Engel, Seckel, Stanev. Sean Grullon

  25. Preliminary Muon Angular Resolution (80 String MC) Median Angular Resolution (After Quality Cuts) ~ 0.557 Degrees! Sean Grullon

  26. Preliminary Muon Energy Resolution (80 String MC) IceCube Preliminary ~20% Narrow Central Peak, but with wide tails. Needs more work. Sean Grullon

  27. Neutrino Effective Area Sean Grullon

  28. Muon Effective Area Sean Grullon

  29. Event Selection – 80 String MC NPE ≥ 5 x 105 if cos(θ) ≥ 0.1 NPE ≥ 1 x 105 otherwise GZK m Atmospheric m Cos MC-theta Keep Log10(NPE) Sean Grullon

  30. CR m m Understanding the Atmospheric Muon Background • Many uncertainties in this energy range • Muon Bundles • Unknown Cosmic Ray Composition • Possible contribution of prompt muons from Charm • Use IceTop Surface Array • Use data to tune our MC Sean Grullon

  31. Understanding the Background • Modeling Muon bundles in The Cosmic Ray Background: E0 Fit with the IC data m = Slope EB Emi Min. Energy in a bundle Sean Grullon

  32. Understanding the BG: GZK and atmospheric muon fluxes revisted The Empirical Model (with “suggested” para. values) Fitting of the Model MC with Data is underway

  33. Energy Calibration • A 337 nm laser deployed on String 40 (The Standard Candle) provides an absolutely calibrated photon source resembling 1PeV cascades. • Golden-DOMs provide a full sensitivity test and absolute calibration. SC s40 GD s39 Sean Grullon

  34. The Standard Candle Built by UC Berkeley Pressure Vessel Emits 337nm photons by the C angle Optics Laser Electronics

  35. Log Npe GZK m Atmospheric m GZK t 107 1010 [GeV] 107 1010 [GeV] 107 1010 [GeV] NPE – Energy Correlation (80 string MC) A. Ishihara astro-ph/0611794 Sean Grullon

  36. Line fit • First guess for tracks • Input: hit time (ti), hit location (ri), Amplitude (Ai) • Ignores Cherenkov cone, ice properties • Light travelling in velocity V • minimze c2 to obtain ‘velocity’ V and ‘vertex’ r • Magnitude of V is the mean speed of the light propogating through a 1-dimensional detector projection. Sean Grullon

  37. Preliminary Angular Resolution Azimuth angle Zenith angle Azimuth angle Zenith angle IceCube Preliminary σ=1.3 deg. σ=0.9 deg. Aspen Cosmic Ray Workshop April 18th 2007

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