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Strategies in the search for astrophysical neutrinos

Strategies in the search for astrophysical neutrinos. Yolanda Sestayo, MPI-k Heidelberg for the IceCube collaboration VLV ν T 09, Athens. AMANDA/IceCube searches for extraterrestrial neutrinos. AMANDA: E > 100 GeV IceCube: E > ~ TeV. Energy Range.

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Strategies in the search for astrophysical neutrinos

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  1. Strategies in the search for astrophysical neutrinos Yolanda Sestayo, MPI-k Heidelberg for the IceCube collaboration VLVνT 09, Athens

  2. AMANDA/IceCube searches for extraterrestrial neutrinos • AMANDA: E > 100 GeV • IceCube: E > ~ TeV Energy Range AMANDA: operation period between 1997-2009 (Abbasi et al. 2009) IceCube • 2006-2007: 9 strings (Finley et al. 2008ICRC) • 2007-2008: 22 strings (Abbasi et al. 2009) • 2008-2009: 40 strings (data is being analyzed) • 2009-2010: 59 strings (taking data) 2006-2007: AMANDA DAQ integrated into IceCube DAQ (Gross et al. 2008ICRC) IceCube + AMANDA • IC22 strings + AMANDA (Portello-Roucelle et al. 2009ICRC) • IC40 strings + AMANDA (data is being analyzed) FUTURE:IceCube + DeepCore

  3. POINT SOURCE SEARCH STRATEGIES • Binned method: samples the sky in angular bins centered in a grid of points of 0.25o x 0.25o. • Unbinned method: test the hypothesis of signal neutrinos from single point sources located at the positions of the grid. Constructs the likelihood assuming a signal pdf following a gaussian plus an energy term. • Steady sources: No time dependence expected • (supernova remnants, pulsar wind nebula, etc) • Time-varying sources: Analysis optimized by a priori information on the variability • (micro-qso, blazars, etc)

  4. SEARCH METHODS: ALL-SKY SEARCH Unbinned analysis ~TeV < E < few PeV AMANDA 3.8 yrs 100 GeV < E < few PeV IceCube 22 strings Unbinned analysis

  5. SEARCH METHODS: GALACTIC PLANE SCAN Combined IceCube 22 strings + AMANDA analysis 100 GeV < E < few PeV Galactic latitude Unbinned analysis Galactic longitude

  6. SEARCH METHODS: ALL-SKY SEARCH • Best way to find neutrino sources without a known counterpart Large statistical penalties (trial factors) All-sky surveys are based on a point-source search over a grid covering all the sky only sensitive to emission within the model PSF Promising sources are studied in separate analysis Need to develop a method to study extended (non-point source) regions

  7. Galactic Accelerators • Galactic accelerators always associated with regions of massive star formation: • Supernova remnants • Pulsar wind nebula • Micro-qso • Massive stellar winds Cas A, SNR Crab, PWN Microqso Wolf-Rayet star

  8. SEARCH STRATEGIES: EXTENDED REGIONS Cygnus: 850 < l < 700 00 • Angular resolution IceCube 80 strings ~ 1o • IC22 ~ 2o • IceCube extended source: • rather an extended region, comprising several • point sources 900 2700 SUN Motivation: extended regions in the galactic plane Superposition of sources at different distances comprising a relatively large area in the sky

  9. Cygnus Region Cygnus There is the compelling need to develop a method which can be applied efficiently to extended regions such as Cygnus! COMPTEL 1.809 MeV line Pluschke et al. 2001 Beacom & Kistler 2007 Abdo et al. 2007

  10. EXTENDED REGIONS: MULTI POINT SOURCE ANALYSIS (MPS) Cygnus region Cygnus region • GOALS: • To have a method which: • Is model independent • - number of sources/clusters unknown • - shape and location of emission unknown • (clustered + diffuse emission) • 2) Takes advantage of the full signal content • - sensitive to weaker neutrino PSs than • std point source analyses if Nsrc > 1 Astrophysical neutrinos in the region increase the clustering of events Signal events (from astrophysical sources) Background events (atmospheric neutrinos) SIGNAL CASE RANDOM CASE

  11. EXTENDED REGIONS: MULTI POINT SOURCE ANALYSIS (MPS) Cygnus region 2-point correlation function: Quantifies clustering of events as function of the angular separation MPS counts pairs of events as function of the angular distance between the events in the pair Pair of events ≡ (event inside, event) Clustering of events increases the number of close pairs • MPS: • 2-point correlation function of the candidate neutrino events, where: • Primaries: events inside the region • Secondaries: all events

  12. EXTENDED REGIONS: MULTI POINT SOURCE ANALYSIS (MPS) MPS focuses on small scale clustering (close pairs)

  13. EXTENDED REGIONS: MULTI POINT SOURCE ANALYSIS (MPS) Cygnus region 2-point binned sampling of the region at the locations of each of the neutrino events. MPS treats every event inside the region as a point source Single-point binned sampling 2-point binned sampling Relative frequency Relative frequency Companions per bin

  14. ANALYSIS OF THE CYGNUS REGION USING IC22+AMANDA 72o < l < 83o, -3o < b < 4o • Selection of the region: • Most intense γ-ray emission • 8 OB associations 72o < l < 83o, -3o < b < 4o

  15. DISCOVERY POTENTIAL Diffuse limit: MPS = binned search Diffuse limit All-sky search With IC22+AMANDA angular resolution we reach the diffuse limit with more than 4 point sources inside the region

  16. RESULTS PRELIMINARY PRELIMINARY UPPER LIMITS Flux Upper Limit for the whole region of 11o x 7o: 7.29x10-11 TeV cm-2s-1 (90% CL) RESULTS COMPATIBLE WITH A BACKGROUND FLUCTUATION

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