All-flavor Neutrino Point-like Source Search with the ANTARES - - PowerPoint PPT Presentation

All-flavor Neutrino Point-like Source Search with the ANTARES Neutrino Telescope

Giulia Illuminati on behalf of the ANTARES Collaboration ICRC2017- 14/07/2017 – Bexco, Busan, Korea

The ANTARES neutrino telescope:

Detector layout

2

~60 m 450 m Junction boxes

Electro-optical cable

Buoy

• Largest neutrino telescope in the Northern Hemisphere
• First detection line installed in early 2006
• Completed in 2008
• 2475 m depth in the Mediterranean Sea
• 40 km offshore from

T

• ulon
• Three-dimensional array of 885 PMTs
• 12 vertical lines, 25 storeys
• 3 PMTs per storey
• PMT facing 45° downwards

3

The ANTARES neutrino telescope:

Detection principle

• Earth used as shield for atmospheric muons
• Either CC or NC interaction with a nucleus

inside or nearby the detector volume

• Cherenkov radiation detected by the PMTs
• Position, time and charge used to reconstruct

direction and energy Track-like events: νμ (ντ ) neutrino CC interaction near the detector è track Shower-like events: all neutrinos NC νe,ντ CC interaction inside

• r very close to the

detector è shower

• New shower reconstruction mechanism recently released [1]
• Shower-like events included for the first time in a point-like source search with ANTARES

[1] PoS ICRC2015 (2016) 1078

4

All-flavour neutrino point source analysis:

Data sample

] ° [ Ψ ∆

2 −

10

1 −

10 1 10

2

10 Cumulative probability 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Track events Shower events

PRELIMINARY

δ sin

1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1

s)

2

cm

• 1

GeV

8

/(10

S

A

0.5 1 1.5 2 2.5 3 3.5 4

Tracks Showers x 3

PRELIMINARY

Acceptance as a function of the source declination for an E-2 energy spectrum. Probability to obtain a reconstructed angle within ΔΨ between the reconstructed direction with respect to the true Monte Carlo neutrino direction. A neutrino flux with an energy spectrum E-2 is assumed.

• Jan 29, 2007 to Dec 31, 2015
• 2423.6 days of lifetime
• Track and Shower events

Total number of selected events:

Ø 7629 tracks Ø 180 showers

Search method: likelihood

5

log$%&' = * * log +%,-

. /, . + 1.2, . − +%,- ,∈. .

/,

56 = /%789: ;,,=, ⋅ /:?:6-@(B,,=,|D,)

/,

%F = /%789: ;, ⋅ /:?:6-@(B,)

2,

56 = 2%789: D, ⋅ 2:?:6-@(B,,=,|D,)

2,

%F = 2%789: D, ⋅ 2:?:6-@(B,)

G = log$%&' − log$'

Track signal PDFs Track background PDFs Shower signal PDFs Shower background PDFs T est Statistic

Search method: likelihood

6

/, = /%789: ⋅ /:?:6-@ 2, = 2%789: ⋅ 2:?:6-@

Signal PDFs Background PDFs

log$%&' = * * log +%,-

. /, . + 1.2, . − +%,- ,∈. .

δ

RA

)

tr

δ sin(

1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1

Selected track events

100 200 300 400 500 600 700 800

PRELIMINARY

E

Background Signal

7

Search method: strategies

• Full-sky search
• TS evaluated in squares of 1°x1° over the ANTARES visible sky
• Galactic Centre region search
• TS evaluated in squares of 1°x1° over a restricted region

around the GC: ellipse, 15° semi-axis in galactic latitude, 20° semi-axis in galactic longitude PRELIMINARY

[1] arXiv:1405.5303 [2] PoS ICRC2015 (2016) 1081

Free parameters: Ø +56 Ø +%F Ø ;%HI69: Ø D%HI69:

• Candidate list searches
• 106 known astrophysical objects (Pulsars, SNRs, …)
• 13 IceCube tracks from the HESE sample [1][2]
• Sagittarius A* location
• T

ested as an extended source by assuming a Gaussian emission profile of various widths

8

Results: Most significant cluster

Full-sky search

PRELIMINARY

Most significant cluster located at (α,δ) = (343.8°, 23.5°) Post-trial significance: 5.9% or 1.9σ (two-sided convention) Upper limit on the neutrino flux: E2dɸ/dE = 3.8 x 10-8 GeV cm-2 s-1

9

Results: Most significant cluster

Candidate list search – 106 candidates

PRELIMINARY

Most significant cluster located at HESSJ0632+057 location (α,δ) = (98.24°, 5.81°) Post-trial significance: 13% or 1.5σ (two-sided convention) Upper limit on the neutrino flux: E2dɸ/dE = 2.4 x 10-8 GeV cm-2 s-1

10

Results: Most significant cluster

Candidate list search – 13 HESE

PRELIMINARY

Most significant cluster located at (α,δ) = (130.1°, -29.8°) at a distance of 1.5° from the HESE track with ID 3 Post-trial significance: 20% or 1.3σ (two-sided convention) Upper limit on the neutrino flux: E2dɸ/dE = 2.1 x 10-8 GeV cm-2 s-1

11

Results: Most significant cluster

Galactic Centre region search

PRELIMINARY

Other spectral indices (ɣ = 2.1, 2.3, 2.5) and source extensions (σ = 0.5°, 1.0°, 2.0°) tested Most significant clusters located at Ø (α,δ) = (257.4°, -41.0°) for a E-2 spectrum and point-like source Post-trial significance: 60% or 0.5σ (two-sided convention) Ø (α,δ) = (273.0°, -42.2°) for a E-2.5 spectrum and point-like source Post-trial significance: 30% or 1.0σ (two-sided convention)

12

Results: Most significant cluster

Sagittarius A*

PRELIMINARY

Location: (α,δ) = (266.42°, -29.01°) Investigated as a point-like source (σ = 0°) and as an extended source (σ = 0.5°, 1.0°, 2.0°) Largest excess above background found for Ø Point-like assumption Ø Pre-trial significance: 22% or 1.2σ (two-sided convention)

13

Results: Sensitivities and Limits

Full-sky and Candidate list searches

δ sin 1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1 ]

• 1

s

• 2

[GeV cm

90%CL

Φ

2

E

10 −

10

9 −

10

8 −

10

7 −

10

6 −

10

5 −

10

ANTARES 2007-15 sensitivity < 100 TeV)

ν

ANTARES 2007-15 sensitivity (E ANTARES 2007-15 limits (candidate list) ANTARES 2007-15 limits (candidate list for HESE events) declination bands) ° ANTARES 2007-15 limits (1 IceCube 7 years sensitivity [ApJ 835(2017)2 151] < 100 TeV) [ApJ 824(2016)2 L28]

ν

IceCube 3 years MESE sensitivity (E IceCube 7 years limits [ApJ 835(2017)2 151]

PRELIMINARY

Sensitivities and upper limits at a 90% C.L. on the signal flux from the Full-sky and the Candidate list searches

14

Results: Sensitivities and Limits

Galactic Centre region search

δ sin 0.7 − 0.6 − 0.5 − 0.4 − 0.3 − 0.2 − ]

• 1

s

• 2

[TeV cm

90%CL

Φ

2

E 16 18 20 22 24 26 28 30

12 −

10 ×

° = 2.0 σ ° = 1.0 σ ° = 0.5 σ ° = 0.0 σ

PRELIMINARY

δ sin 0.7 − 0.6 − 0.5 − 0.4 − 0.3 − 0.2 − ]

• 1

s

• 2

cm

• 1

γ

[TeV

90%CL

Φ

γ

E

11 −

10

10 −

10

= 2.5 γ = 2.3 γ = 2.1 γ = 2.0 γ

PRELIMINARY

90% C.L. upper limits of the search restricted to the region around the origin of the galactic coordinates at (α,δ) = (266.40°,-28.94°) assuming different spectral indices for the neutrino flux (left) and different source extensions for ɣ= 2 (right).

15

Results: Sensitivities and Limits

Sagittarius A*

] ° [ σ 1 2 3 4 5 6 ]

• 1

s

• 2

[TeV cm

90%CL

Φ

2

E

11 −

10

10 −

10

Sensitivity (assuming width) Sensitivity (assuming point-source) 90% C.L. Limit discovery flux (assuming width) σ 5 discovery flux (assuming point-source) σ 5

PRELIMINARY

Discovery flux (solid red), median sensitivity (dotted blue) and upper limits (solid blue) at 90% C.L. for a search for an extended source at Sagittarius A* at (α,δ) = (266.42°,-29.01°) assuming different angular extensions σ. The dashed lines correspond to the point-like source assumption.

16

Conclusions

Ø First all-flavor neutrino point-like source search with the ANTARES neutrino telescope Ø No significant evidence of cosmic neutrino sources found Ø Full-sky search: largest excess found at (α,δ) = (343.8°, 23.5°) with 1.9σ significance Ø Candidate list search over 106 candidates: largest excess found for HESSJ0632+057 with 1.5σ significance Ø Candidate list search over 13 IceCube HESE: largest excess found HESE with ID 3 with 1.3σ significance Ø Galactic Centre region search: largest excess found at (α,δ) = (257.4°, -41.0°) for a E-2 spectrum and point-like source with 0.5σ significance Ø Sagittarius A*: largest excess found for a point-like source with 1.2σ significance Ø Most sensitive limits for a large fraction of the Southern Sky set, especially at neutrino energies below 100 T eV.

17

Backup

18

Candidate list

arXiv:1706.01857

19

IceCube HESE candidates

arXiv:1706.01857

20

Selection criteria

arXiv:1706.01857

21

Selection criteria

Track-like events selection cuts

§ Quality parameter: Λtr > -5.2 § Estimated angular error: βtr < 1° § Up-going: cosθtr > -0.1 § Energy estimator: log10(J) > 1.6 § Muon track length: Lμ > 360 m

Shower-like events selection cuts

§ T rack veto: not selected as track § Estimated angular error: βsh < 1° § Up-going: cosθsh > -0.1 § Interaction vertex: Rsh < 300 m, |Zsh| < 250 m § M-estimator: Mest < 1000 § Random Decision Forest: RDF > 0.3 § Muon likelihood: Kμ > 50

22

Data/MC comparison

sh

θ cos

0.2 0.4 0.6 0.8 1

DATA/MC

0.5 1 1.5 2 2.5 3

sh

θ cos 0.2 0.4 0.6 0.8 1 Events

1 −

10 1 10

2

10

3

10

Data ν Atm. µ Atm. ν Cosm.

Λ

5.5 − 5 − 4.5 − 4 − 3.5 − 3 −

DATA/MC

0.5 1 1.5 2 2.5 3

Λ 5.5 − 5 − 4.5 − 4 − 3.5 − 3 − Events

4 −

10

3 −

10

2 −

10

1 −

10 1 10

2

10

3

10

4

10

5

10

6

10

selected Data ν Atm. µ Atm. ν Cosm.

Comparison of the data with Monte Carlo simulations as a function of the quality parameter Λ (left) and of the zenith θsh of the reconstructed shower direction.

23

Systematic uncertainties

)

tr

δ sin(

1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1

Selected track events

100 200 300 400 500 600 700 800

PRELIMINARY

)

sh

δ sin(

1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1

Selected shower events

5 10 15 20 25 30 35

PRELIMINARY

• Absolute Pointing Accuracy Uncertainty

0.13° uncertainty on the horizontal (ϕ) direction 0.06° uncertainty on the vertical (L) direction

• Angular Resolution Uncertainty

15% (12%) degradation on the angular resolution in the track (shower) channel

• Acceptance Uncertainty

15% uncertainty

• Background Uncertainty

declination-dependent distribution of background events parameterized as a linear combination of the two different spline functions (the red and blue lines)