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

AMANDA/IceCube searches for extraterrestrial neutrinos Energy Range AMANDA: E > 100 GeV IceCube: E > ~ TeV AMANDA: operation period between (Abbasi et al. 2009) IceCube : 9 strings (Finley et al. 2008ICRC) : 22 strings (Abbasi et al. 2009) : 40 strings (data is being analyzed) : 59 strings (taking data) : 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

POINT SOURCE SEARCH STRATEGIES Binned method: samples the sky in angular bins centered in a grid of points of 0.25 o x 0.25 o. 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)

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

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

SEARCH METHODS: ALL-SKY SEARCH Best way to find neutrino sources without a known counterpart 1.Large statistical penalties (trial factors) 2.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 1.Promising sources are studied in separate analysis 2.Need to develop a method to study extended (non-point source) regions

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, PWNMicroqso Wolf-Rayet star

Angular resolution IceCube 80 strings ~ 1 o IC22 ~ 2 o IceCube extended source: rather an extended region, comprising several point sources SEARCH STRATEGIES: EXTENDED REGIONS 0 Cygnus: 85 0 < l < 70 0 SUN Motivation: extended regions in the galactic plane Superposition of sources at different distances comprising a relatively large area in the sky

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

EXTENDED REGIONS: MULTI POINT SOURCE ANALYSIS (MPS) GOALS: To have a method which: 1)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 Cygnus region Astrophysical neutrinos in the region increase the clustering of events RANDOM CASE Signal events (from astrophysical sources) Background events (atmospheric neutrinos) SIGNAL CASE

Cygnus region EXTENDED REGIONS: MULTI POINT SOURCE ANALYSIS (MPS) 2-point correlation function: Quantifies clustering of events as function of the angular separation MPS: 2-point correlation function of the candidate neutrino events, where: Primaries: events inside the region Secondaries: all events 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

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

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 Cygnus region EXTENDED REGIONS: MULTI POINT SOURCE ANALYSIS (MPS) Single-point binned sampling 2-point binned sampling Companions per bin Relative frequency

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

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

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