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Overview

Overview. Astrophysical Neutrinos & Searching for a Diffuse Flux of Muon Neutrinos Muon Energy Estimation 22 String Diffuse Analysis Results Outlook for 40 Strings Questions & Discussion. Neutrinos as Cosmic Messengers. Neutrinos help answer many questions in astrophysics:.

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Overview

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  1. TeV Particle Astrophysics 2009 Stanford Linear Accelerator Laboratory

  2. Overview • Astrophysical Neutrinos & Searching for a Diffuse Flux of Muon Neutrinos • Muon Energy Estimation • 22 String Diffuse Analysis Results • Outlook for 40 Strings • Questions & Discussion Sean Grullon – TeVPA 2009

  3. Neutrinos as Cosmic Messengers Neutrinos help answer many questions in astrophysics: • What are the sources of highest energy cosmic rays? Are there pp and p interactions at the source? • Can neutrino production be linked to TeV  sources, GRBs, AGN? • Can a superposition of faint neutrino sources cause a detectable signal? Sean Grullon – TeVPA 2009

  4. 2007-2008: 18 Strings 2006-2007: 13 Strings 2005-2006: 8 Strings 2004-2005 : 1 String IceTop Air shower detector threshold ~ 300 TeV InIce first data 2005 upgoing muon 18. July 2005 80-86 Strings, 60 Optical Modules per String AMANDA 19 Strings 677 Modules Sean Grullon – TeVPA 2009

  5. Cosmic ray Atmosphericm n Atmospheric n m Astrophysical (signal) n Sean Grullon – TeVPA 2009

  6. Downgoing Muon Rejection • Apply quality cuts on Data, Corsika MC, andAtmospheric Neutrino MC Sean Grullon – TeVPA 2009

  7. Diffuse Analysis Strategy • Find an excess of astrophysical neutrinos (E-2) over atmospheric neutrinos (E-3.7) at the high-energy tail of an energy distribution Sean Grullon – TeVPA 2009

  8. m p e+e- photo-nuclear g pair-creation bremsstrahlung Energy Estimation • Convert what is measured, Cherenkov light, to an estimate of the Muon energy. • Simplest estimation: Number of Triggered Optical Modules (NCh) • More Sophisticated: Muon Energy Loss (dE/dX) Sean Grullon – TeVPA 2009

  9. dusty clean shallow deep Reconstructing The Muon energy loss Formulate LLH: Approximate as: Incorporate Ice Properties: Sean Grullon – TeVPA 2009

  10. Muon Energy Correlation – 40 Strings dE/dX Reco NChannel • dE/dX reco more linearly correlated with Muon energy Sean Grullon – TeVPA 2009

  11. Energy Resolution – 40 Strings Width 0.27 Width 0.43 • dE/dX reco has narrower energy resolution Sean Grullon – TeVPA 2009

  12. Energy Resolution as a Function of Muon Energy – 40 Strings Sean Grullon – TeVPA 2009

  13. The dE/dX distribution of IC22 275.7 days LiveTime • Find cut that minimizes • average upper limit • Energy Cut > 1.4 • Background above cut • = 4.1 Events • Observed Data above cut • = 4.0 Events Keep • Sensitivity: • 2.5 x10-7 • GeV cm-2 s-1 sr-1 Sean Grullon – TeVPA 2009

  14. The dE/dX distribution of IC40 300 days LiveTime - MC Only Sean Grullon – TeVPA 2009

  15. Likelihood Analysis Method • Likelihood - product over bin-by-bin Poisson probabilities: Events observed in bin i Events expected in bin i Conventional Atmospheric ν Prompt ν Astrophysical ν Sean Grullon – TeVPA 2009

  16. Fitting Example: 1 Year IC40 - No Astrophysical or Prompt ν • “Data” Poisson sampled • from 1 year of Atm. ν MC Sean Grullon – TeVPA 2009

  17. Allowed Regions, No Astrophysical or Prompt ν : 1 Year of IC40 Preliminary IC40 Diffuse Sensitivity: E2 < 1.1 x 10-8 GeV cm-2 s-1 sr-1 No Systematics included Sean Grullon – TeVPA 2009

  18. Models & Limits IC22 WB IC40 Sean Grullon – TeVPA 2009

  19. Summary • A reliable log-likelihood reconstruction of the muon energy loss is now available for IceCube analyses. • The IC22 sensitivity is E2 < 2.5 x 10-8 GeV cm-2 s-1 sr-1above a dE/dX cut of log10(dE/dX) >= 1.4 • 275.7 days of IC22 data were analyzed and compared with the Bartol + naumov RQPM atmospheric neutrino simulation. No data excess over the atmospheric neutrino prediction observed above the dE/dX cut. • The IC40 analysis uses a likelihood method giving a preliminary sensitivity of E2 < 1.1 x 10-8 GeV cm-2 s-1 sr-1 and the incorporation of systematic errors is currently underway. Sean Grullon – TeVPA 2009

  20. Backup slides Sean Grullon – TeVPA 2009

  21. Systematics – IC22 • Observed data exceeds MC by a factor of 2 in deep ice • Deep Ice 40% clearer. New from IceCube AMANDA depth Data Atms. Nu MC Coinc. Mu Single Mu Sean Grullon – TeVPA 2009

  22. Systematic Test (low energy, NCh<50) Data Atms. Nu MC COGZ COGZ • Data excess is observed even with the low energy events(conventional atmospheric neutrinos) • Divide the detector in 2 depths : upper half and lower half upgoing cos(zenith) horizon upgoing cos(zenith) horizon Data - MC COGZ Sean Grullon – TeVPA 2009

  23. Systematic Test Upper Half Lower Half Sean Grullon – TeVPA 2009

  24. Sensitivities: Likelihood Method Extraterrestrial Only Sean Grullon – TeVPA 2009

  25. Fitting Example: No Signal Sean Grullon – TeVPA 2009

  26. Fitting Example: No Signal Sean Grullon – TeVPA 2009

  27. Allowed Signal and Prompt Regions Sean Grullon – TeVPA 2009

  28. Fitting Example: Signal + Prompt + Conventional Atmospheric Neutrinos “Data” sampled from Atm Nu background Sean Grullon – TeVPA 2009

  29. Allowed Extraterrestrial and Prompt Regions Sean Grullon – TeVPA 2009

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