NEUTRINO POINT-SOURCE ANALYSIS IN ICECUBE … · NEUTRINO POINT-SOURCE ANALYSIS IN ICECUBE Juan...

Vulcano Italy, 2010

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IC40 All-Sky Stacking Conclusions

NEUTRINO POINT-SOURCE

ANALYSIS IN ICECUBE

Juan Antonio Aguilar

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IC40 CONFIGURATION

Juan Antonio Aguilar Vulcano Workshop 2010

ICECUBE

IceCube 59 (2009-10)

IceCube 40 (2008-9)

IceCube IC59 data is being processed. Analysis starting now.

IC40 has approx. 2 x effective area of the previous IC22. IC40 data has been analyzed for point sources.

Completion with 80 (+ 6) strings by January 2011

IceCube

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IceCube 79 (2010)79 strings are in operation.



IC40 MUON SAMPLE

L3 (muon sample)

Trigger

L2 (muon filter)

Strings Year LivetimeSMT rate (Hz)

µ filter rate (Hz)

atm. ν final rate

9 2006 137 d 80 6 1.7

22 2007 276 d 450 20 18/d

40 2008 375.5 d 1100 23 40/d

59 2009 320 d 1900 24

79 2010 2300 40

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IC40 rate evolutionDetector rates:

Atm. neutrinos Atm. muons


Upgoing Downgoing


IC40 MUON SAMPLE

L3 (muon sample)

Trigger

L2 (muon filter)

Strings Year LivetimeSMT rate (Hz)

µ filter rate (Hz)

atm. ν final rate

9 2006 137 d 80 6 1.7

22 2007 276 d 450 20 18/d

40 2008 375.5 d 1100 23 40/d

59 2009 320 d 1900 24

79 2010 2300 40

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IC40 rate evolutionDetector rates:

Atm. neutrinos Atm. muons

Get all sky cutting on total charge


Upgoing Downgoing


ANGULAR RESOLUTIONCumulative distribution of the Point Spread Function for different IceCube configurations:

50% angular resolution

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Top view

‣IC40 has already in one direction a size equals to IceCube (IC80)

IC40


EFFECTIVE AREASolid-angle averaged neutrino effective area:

The smaller the zenith, the more sensitive to higher

energies.

South Pole

180-150

150-120

120-90

60-90

30-60

0-30


There is a factor 2 increase at high energy and > 8 at low energies.

IC80+DC6, ϴ = (120◦ - 90◦)IC80+DC6, ϴ = (150◦ - 120◦)IC80+DC6, ϴ = (180◦ - 150◦)IC40, ϴ = (120◦ - 90◦)IC40, ϴ = (150◦ - 120◦)IC40, ϴ = (180◦ - 150◦)

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ALLSKY ANALYSIS


LIKELIHOOD AND DENSITY FUNCTIONSLikelihood Space around track solution fit to paraboloid: width = σSignal pdf:

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!"#$

!" %&'()$


LIKELIHOOD AND DENSITY FUNCTIONS

Signal pdf:

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Signal pdf:

Scrambled real data

Background pdf:

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Likelihood:

Background pdf:Signal pdf:

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Likelihood:

Background pdf:

Maximization of the likelihood ratio:

€

logλ = log L( ˆ γ , ˆ n s)L(ns = 0)

Estimates that

maximize the Likelihood

The final significance is determined by scrambling the data in r.a. and repeating the analysis.

Signal pdf:

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Two main components in the final analysis sample:-The Southern sky (downgoing atm. muons) has a better angular resolution. -The Northern sky (upgoing atm. neutrinos) has a lower energy range.

Northern Sky Southern Sky


IC40 ALLSKY ANALYSIS SAMPLE


Paper published by ApJL, 701:L47, 2009

24h

+30°

+15°

+45°

+60°+75°

-log 1

0 p

Atm

. neu

trin

os

IC22 ALL SKY RESULTS

Hottest spot found at r.a. 153.4° , dec. 11.4°

Post-trials p-value of analysis is ~ 1.34% (2.2 sigma)

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-log 1

0 p

IC22 ALL SKY RESULTS

0h24h

+30°

+15°

+45°

+60°+75°

‐15°

‐30°

‐45°

Atm

. neu

trin

osA

tm. m

uons

Analysis extended to ‐50° dec

Paper published by Phys. Rev. Lett. 103, 221102 (2009)

First IceCube search for point sources above the horizon optimized for higher energies

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IC40 EVENT MAPA

tm. n

eutr

inos

Atm

. muo

ns

Jon Dumm

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‣Livetime: 375.5 days‣Events: 37290 (14139 up-going, 23151 down-going)


IC40 SIGNIFICANCE MAPA

tm. n

eutr

inos

Atm

. muo

ns

‣Log-likelihood is calculated on a fine grid: 0.1° x 0.1°‣Significance comes from the hottest single spot, calculated as the fraction of scrambled trials with equal or higher significance – robust result

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Preliminary

Jon Dumm


IC40 SIGNIFICANCE MAPA

tm. n

eutr

inos

Atm

. muo

ns

‣Log-likelihood is calculated on a fine grid: 0.1° x 0.1°‣Significance comes from the hottest single spot, calculated as the fraction of scrambled trials with equal or higher significance – robust result

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Preliminary

Jon Dumm

Ho#est loca+on in the all‐sky search is:

Ra=115.05, Dec=15.05


IC40 ALLSKY RESULTS

‣ The distribution of results for 10000 scrambled skymaps.

‣ For each scrambled trial, the same analysis is performed.

‣ The hottest spot in each trial yields the -log10(pmin) that goes into this histogram. 9588 of the 10000 scrambled skymaps had a -log10(pmin) equal or greater than that of the real dataset ➜ all‐sky p‐value = 96%.

2016


observed value

96%


UPPER LIMITS (90% CL)

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‣Median Neyman sensitivities/UL for E-2 neutrino spectrum‣Discovery potential at 5σ (P = 50%) takes ~3x more flux‣IceCube (IC86) ~2x better than IC40

Preliminary


SPECTRAL INDEX

1-sigma

E-3

E-2

E-1.5

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Number of events for a 50% discovery potential

How well we can fit the spectral index depends on the number of signal events. Softer spectrum require higher number of events to claim a a discovery.



‣Analysis is optimized for E-2 spectra.

‣Gamma spectra from galactic sources exhibit cut-offs at energies of about 5-30 TeV.

‣Southern sky is more sensitive to a cut-off. But we are still sensitive in the Northern hemisphere even if we loose sensitivity for cut-offs < 100 TeV

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SPECTRUM CUTOFF

€

dΦ /dE =Φ0E −2 exp(−E /Ecutoff )

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STACKING ANALYSIS


STACKING ANALYSIS‣ Combine the signal from similar sources: Stacking

‣ Small modification in the PS search:

‣ The gain by adding more identical sources is somewhere between:

- √nSources ➜ expectation for high background

- nSources ➜ expectation for low background


Sum of signal pdf


MILAGRO-FERMI SOURCES: THE GEV – TEV CONNECTION

Abdo et al. 2009, arXiv:0904.1018v3

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‣Milagro showed that many Fermi GeV gamma ray sources extend to TeV‣Of 34 galactic Fermi BSL sources in Milagro 6 (14) are observed with > 5 (3) σ‣Probability of 4 or more excesses > 3 σ in 34 trials is p = 1.5 x 10-7 ‣Strong evidence for multi-TeV emission from Galactic BSL sources as a class.


NEARBY CLUSTER OF GALAXIES

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Name Size (°)RA(°) Dec(°)Virgo 8.0 186.6 12.7Centaurus 1.2 193.2 ‐41.3Perseus 2.4 50.0 41.5Coma 1.8 195.0 28.0Ophiuchus 0.9 247 ‐24.5


Murase et al. 2008, arXiv:0805.0104v2:

‣Cluster of Galaxies (CG) might explain CR between the second knee and the ankle.‣Different models CR density predicts neutrino emission.‣Detection of individual neutrino signal is still challenging for IceCube-like detectors ➜ Stacking.


Stacked Sources (# of

sources)

P-value from scrambling

Fit Number of Source

Events

Fit SpectralIndex

90% Upper Limit

(10−12TeV−1cm−2s−1)

Milagro (17) 41.2% 4.2 -2.8 8.0

Nearby Clusters (5) 82.0% 0.6 -3.9 10.6

Starbursts Galaxies (127)

28.1% 2.9 -2.3 36.5

IC40 STACKING RESULTS

Dense ISM ➜ Elevated star formation rates ➜ SNR ➜ CR ➜ Neutrinos Becker et al. 2009, arXiv:0901.1775v1

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Preliminary


STACKING 6 MILAGRO SNRIC40 Stacking Search Med. Sensitivity 90% Upper Limit

Milagro 6 SNR 2.05 * prediction 5.50 * prediction

3.0 events in IC40 predicted by flux from Halzen et al. 2008, arXiv:0803.0314v2

AMANDA 7-yr IC22 IC40

20% 27% 2.3%

p-values of 6 Milagro SNR stacked searches:

(a posteriori)

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Preliminary

Will be tested again in future detector configurations…

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CONCLUSIONS


CONCLUSIONS

• IceCube is starting the IC79 data taking and IC59 data analysis has started.

• The whole year of IC40 has been analyzed for point-source and no evidence of a neutrino point source has been found.

• By stacking similar sources we can enhance the sensitivity/discovery potential.

• IceCube has already a sensitivity 10 times better than any neutrino telescope in its preferred hemisphere and with IC40 we have started the extension to all-sky analysis.

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NEUTRINO POINT-SOURCE ANALYSIS IN ICECUBE … · NEUTRINO POINT-SOURCE ANALYSIS IN ICECUBE Juan...

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