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Search for EHE neutrinos with the IceCube detector

Search for EHE neutrinos with the IceCube detector. Aya Ishihara for the IceCube collaboration Chiba University. atmospheric muon flux above 10 6 GeV is very uncertain. EHE Neutrino Underground. Surface n fluxes. Target GZK neutrino Surface energy range 8 < Log(E/GeV) < 12

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Search for EHE neutrinos with the IceCube detector

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  1. Search for EHE neutrinoswith the IceCube detector Aya Ishihara for the IceCube collaboration Chiba University

  2. atmospheric muon flux above 106GeV is very uncertain EHE Neutrino Underground Surface n fluxes Target GZK neutrino Surface energy range 8 < Log(E/GeV) < 12 (energy at depth ~ 6-7< Log(E/GeV) < 10-11) atm m Fluxes at the IceCube depth main signal GZK neutrino induced leptons background Atmospheric muon Simple energy cut works! EGZK>>EAtm m S. Yoshida et. al. (2004) Phys. Rev. D 69 103004

  3. 9 EeV ? Energy ! mandttracks loose their energy by radiative processes 100 TeV pair-creation e+e- m p photo-nuclear e+e- m g bremsstrahlung

  4. The 9-stringreal sample2006Example Bright Events 20mV 0mV [ns] Digital optical module waveform (ATWD / FADC) NPE = integral of waveforms / single charge

  5. m t NPE and Energy Correlationwith 2006 IceCube configuration Visible Energy vs. NPE correlation up to log10 NPE ~ 4.5 the resolution is then diffused by waveform saturation effects log ( m Energy / GeV ) log ( t Energy / GeV )

  6. m Atmospheric Muon Bundles Model Number of muon in a shower above threshold Energy Ethres (Elbert parameterization) This relation between cosmic ray energies and the energy of the muon bundle fixes atmospheric muon bundle fluxes log Cosmic-Ray Energy Nagano, Watson: Reviews of Modern Physics Vol 72 No3 (689)

  7. Background simulation Partial experimental data atmospheric m simulation model 1 atmospheric m simulation model 2 log10NPE cos q 4 < log10NPE < 5

  8. Atmospheric fluxes at IceCube depth #2 #1 without GZK cutoff with GZK cutoff !! #1 #1

  9. Comparison with CORSIKA Atmospheric m empirical model Corskia Proton QGSJET01 Corsika Iron QGSJET01 log (m Bundle Energy at Depth [GeV]) log (Primary CR Energy [GeV]) proton and ion both underestimate the rate overestimate underestimate m bundle energy 10 PeV m bundle energy 1 PeV m bundle energy 100 TeV log (Primary CR Energy [GeV])

  10. Event Selection and Numbers number of events Atm. m GZK m GZK t

  11. Sensitivity for 2006 E2 fcut2 (106.5 < E < 109.5) ~ 10-6 [GeV cm-2 sr-1 sec-1] 90 % C.L. all n flavors added assuming 1:1:1 ratio

  12. Neutrino Effective Area average over full solid angle Cut level 2

  13. Summary • The IceCube 9 string array provided physics data sample in 2006 • MC shows 9 string IceCube is capable of EHE neutrino search but waveform saturation and its readout limits its capability • For BG estimation, Elbert formula, derived from experimental relation between EHE CR fluxes and surface mu bundle energy, used • Effective area, sensitivity of ~10-6 [GeV cm-2 sr-1 sec-1] for 2006 IceCube EHE region is obtained with optimized cuts with the assumption of zero background events from the empirical atmospheric m background model

  14. backup

  15. Comparison with CORSIKA Proton QGSJET01 Iron QGSJET01

  16. The 9-stringreal sample2006FADC Waveforms saturated

  17. NPE 20mV 0mV Integrating a waveform/single charge = NPE low gain EHE waveforms high gain 120mV 0mV + = 4.5V 0V 4.5V 0V

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