THE KM3NET/ARCA DETECTION CAPABILITY TO A DIFFUSE FLUX OF COSMIC - - PowerPoint PPT Presentation

THE KM3NET/ARCA DETECTION CAPABILITY TO A DIFFUSE FLUX OF COSMIC NEUTRINOS

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• R. Coniglione for the KM3NeT collaboration

INFN - LNS Catania (Italy)

KM3NeT

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KM3NeT/ARCA (Astroparticle Research with Cosmics in the Abyss)

¤ discovery and observation of high energy (GeV ÷ PeV) neutrino sources

☛ a telescope offshore Capo Passero (Sicily-Italy) is in construction at a depth of 3500m

KM3NeT/ORCA (Oscillation Research with Cosmics in the Abyss)

¤ determination of the neutrino mass hierarchy 👊 a detector offshore

Toulon (France) able to detect neutrinos of tens of GeV is in construction at a depth of 2500m

ORCA and ARCA same detector technology

KM3NeT is a distributed research infrastructure in the Mediterranean Sea hosting neutrino detectors

Highlight talk by Aart Heijboer 👊 July 19th(Wed.) ORCA Talk by Antoine Kouchner 👊 July 15th(Sat.)

The KM3NeT/ARCA design

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2 building blocks of 115 Detection Units (DU) each (0.5 km

3/block)

Each DU with 18 Digital Optical Modules (DOM). Power and data distributed by a single backbone cable with breakouts at DOMs Sea network of submarine cables and Junction Boxes connected to shore via a main electro-optical cable First two DUs already installed and first data analyzed

The optical sensor: Digital Optical Module (DOM). Each DOM comprises 31 3’’ PMTs The Detection Unit (DU)

a 3D array of optical sensors

Talk on first ARCA results by Martijn Jongen 👊 July 13th(Thur.)

36m 90m

Event classes in a neutrino telescope

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“Track-like” events mainly from vμ CC interactions “Cascade-like” events mainly from ve CC and NC interactions Track reconstruction algorithm Cascade reconstruction algorithm Track analysis - up-going events Cascade analysis - full sky - contained events

👈 👈 👈 👈

Observation time [years] 0.5 1 1.5 2 2.5 3 3.5 ] σ Significance [ 1 2 3 4 5 6

• 2

cm

• 1

s

• 1

sr

• 1

exp(-E/3 PeV) GeV

• 2

(E/1 GeV)

• 8

flux per flavour 1.2 10

tracks cascades combined conventional uncertainty

atm

ν prompt uncertainty

atm

ν

KM3NeT

A telescope in the Northern hemisphere for the observation of diffuse cosmic neutrinos

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Existence of astrophysical neutrinos proven by IceCube 6 year analysis with up-going tracks (Astrophys. J. 833 no.1 - 2016) 👊spectrum ∝ E

• 2.13

Combined analysis (Astrophys. J. 809 no.98 - 2015) 👊 spectrum ∝ E

• 2.5

Evidence for a multicomponent spectrum (Galactic + extragalactic ?)

Estimate of the ARCA performances for diffuse and neutrinos sources in the published Letter of Intent

• update on diffuse flux in this talk
• update on point-like sources in poster

session expected ARCA performances for a diffuse flux (from LoI)

What’s new since the LoI

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Update of results for diffuse from all-sky and

Galactic Plane region

new track reconstruction algorithm better angular resolution higher efficiency Multi-variate analysis (Scikit-learn)

Talk on ARCA reconstruction algorithms by Karel Melis 👊 July 13th(Thur.)

Two assumed benchmark fluxes (same fluxes as the LoI)

All-sky analysis with tracks

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Benchmark fluxes compatible with the measured IceCube fluxes

Analysis steps Pre-selection cut on events reconstructed as up-going or

few degrees above the horizon (θzen>85° optimized)

Multivariate analysis 👊 Scikit-learn distinguish between three event samples (μatm, νatm, νsign) 11 “features” to train the algorithm 👊 from the

reconstruction code or from the topology of the events

Max likelihood

Psig and Pbkg are the probability density function (PDF) for signal and background events estimated from the multivariate analysis as probability to belong to the “signal” class nsig number of expected events in the detector

1 flavour fluxes

All-sky analysis: results

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• bservation years

1 2 3 4 5 6

)

• 1

sr

• 1

s

• 2

(GeV cm Φ

9 −

10

8 −

10

exp(-E/3PeV)

• 2

E Φ flux

50% σ 3 50% σ 5

KM3NeT ARCA Preliminary

• bservation years

1 2 3 4 5 6

)

• 1

sr

• 1

s

• 2

(GeV cm Φ

7 −

10

6 −

10

5 −

10

• 2.5

E Φ flux

50% σ 3 50% σ 5

KM3NeT ARCA Preliminary

Discovery fluxes as a function of the observation years

About one year to reach a 5σ discovery for E-2 spectrum with cutoff* and less if the spectrum is softer (E-2.46 no cutoff) flux ɸ0 E-2.46 flux ɸ0 E-2 exp(-E/3PeV)

*in the LoI 1.5 years

Analysis steps Track analysis Pre-selection cut on events reconstructed as up-going or

few degrees above the horizon θzen>80°

Max likelihood Cascade analysis Selected events with the reconstructed vertex inside the

detector geometry

according to the reconstructed zenith angle from the

tracking algorithm, events are classified as upward- going (sample “A”, cosθtrack > -0.4) or downward-going (sample “B”, cosθtrack < -0.4).

Cut on the total Time-over-Threshold (related to the

total charge of the hits) of the event to reject low energy events on both samples

Random Decision Forest Max likelihood

• Neutrino flux (one flavour) estimated from a non uniform cosmic-ray transport model with

a radially dependent diffusion coefficient (same flux as the LoI)

Galactic plane region |l|<30° |b|<4°

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• D. Gaggero et al.,2015. arXiv:1508.03681. ICRC2015

3 flavour flux

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Discovery fluxes and sensitivity as a function of the observation years

About 4 years to reach a 5σ discovery both for track and cascade analysis*

Galactic plane region |l|<30° |b|<4°

Observation years

1 2 3 4 5

)

• 1

sr

• 1

s

• 2

(GeV cm Φ

6 −

10

5 −

10

) E/1 PeV exp(-

• 2.3

(E/1GeV) Φ flux

50% σ Track - 5 50% σ Track -3 Track -sensitivity 90% C.L. 50% σ Cascade - 5 50% σ Cascade - 3 Cascade - sensitivity 90% C.L.

KM3NeT ARCA preliminary

*in the LoI 4.8 years for track analysis cascade analysis not presented in the LoI

Comparison

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|b| < 3° and |l|<30° Improvement expected combining cascade + track events ANTARES Upper Limit 7y (ArXiv:1705.00497v1*) KM3NeT track analysis (same values for cascade analysis) discovery 3σ 4y sensitivity 4y

*region |b|<3° |l|<40°

Summary

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Update of the results presented in the LoI for diffuse emission from all sky and Galactic Plane region

all-sky search 👊 improvement of about 0.5 year for the

5σ discovery all-sky with tracks

GP region |l|<30° |b|<4° track analysis 👊 improvement of about 1 year for the

5σ discovery

cascade analysis 👊 new estimates for the cascade

analysis give similar results to the track analysis

Analysis not yet completed 👊 better results expected combining cascade with track events

Conclusions

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KM3NeT/ARCA can observe the diffuse high energy neutrino

flux in few years from a different field of view and with different systematic uncertainties

With its good angular resolution (<0.1°@ Eν>100 TeV) it can

better discriminate the emitting region in the sky thus helping in the understanding of the origin of the observed astrophysical neutrinos