Search for supernova relic neutrinos at Super-Kamiokande - TAUP
Strategies in the search for astrophysical neutrinos
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Strategies in the search forStrategies in the search forastrophysical neutrinosastrophysical neutrinos
Yolanda Sestayo, MPI-k Heidelbergfor the IceCube collaboration
VLVνT 09, Athens
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AMANDA/IceCube searches for extraterrestrial neutrinos
Energy Range • AMANDA: E > 100 GeV
• IceCube: E > ~ TeV
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
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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)
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SEARCH METHODS: ALL-SKY SEARCHAMANDA 3.8 yrs
100 GeV < E < few PeVUnbinned analysis
IceCube 22 strings~TeV < E < few PeV
Unbinned analysis
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SEARCH METHODS: GALACTIC PLANE SCAN
Unbinned analysis
Combined IceCube 22 strings + AMANDA analysis100 GeV < E < few PeV
Gal
actic
latit
ude
Galactic longitude
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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 analysis2. Need to develop a method to study extended (non-point
source) regions
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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
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• Angular resolution IceCube 80 strings ~ 1o
• IC22 ~ 2o
IceCube extended source:
rather an extended region, comprising several point sources
SEARCH STRATEGIES: EXTENDED REGIONS
00
Cygnus: 850 < l < 700
SUN
900 2700
Motivation: extended regions in the galactic planeSuperposition of sources at different distances comprising a relatively large area in the sky
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Cygnus Region
Cygnus
COMPTEL 1.809 MeV line Pluschke et al. 2001
Abdo et al. 2007
There is the compelling need to develop a method which can be applied efficiently to
extended regions such as Cygnus!
Beacom & Kistler 2007
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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 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
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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
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EXTENDED REGIONS: MULTI POINT SOURCE ANALYSIS (MPS)
MPS focuses on small scale clustering(close pairs)
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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
Rela
tive
freq
uenc
y
Rela
tive
freq
uenc
y
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ANALYSIS OF THE CYGNUS REGION USING IC22+AMANDA
72o < l < 83o, -3o < b < 4o
72o < l < 83o, -3o < b < 4o
Selection of the region:
• Most intense γ-ray emission
• 8 OB associations
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DISCOVERY POTENTIALDiffuse 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
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UPPER LIMITSFlux Upper Limit for the whole region of 11o x 7o: 7.29x10-11 TeV cm-2s-1 (90% CL)
RESULTS
PRELIMIN
ARY
RESULTS COMPATIBLE WITH A BACKGROUND FLUCTUATION
PREL
IMIN
AR
Y