Recent Results of the Acoustic Neutrino Detection Test System AMADEUS

Robert Lahmann for the ANTARES Collaboration ICRC 2013, Rio de Janeiro, 4-Jul-2013

Motivation

AMADEUS: Acoustic Neutrino Test System in ANTARES Main objective: feasibility study for a potential future large-scale acoustic neutrino detector •  Investigate background conditions •  Determine energy threshold for neutrino detection •  Devise high efficiency, high purity neutrino detection

algorithms

Acoustic Neutrino Detection: Main science case: cosmogenic neutrinos

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Acoustic Detection of Neutrinos

3

-0.08-0.06-0.04-0.02

0 0.02 0.04 0.06 0.08

0.1 0.12

-0.04 -0.02 0 0.02 0.04Pr

essu

re [P

a]

Time [ms]

1011GeV @ 1000m

Hadronic cascade: ~10m length, few cm radius Pressure field: Characteristic “pancake” pattern Long attenuation length (~5 km @ 10 kHz)

Thermo-acoustic effect: (Askariyan 1979) energy deposition ð local heating (~µK) ð expansion ð pressure signal

ν ~1o

Time [ms]

Pres

sure

[Pa]

The AMADEUS System of the ANTARES detector�

ANTARES site

AMADEUS : •  Total of 6 “acoustic storeys” •  Total of 36 hydrophones •  Continuous sampling •  Online filter selects ~1% of data volume for storage

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ANTARES site: •  2500m depth, 30km offshore

Background for Acoustic Detection in the Sea Transient background

Bipolar Pressure Signals (BIPs)

ðDetermines fake neutrino rate ðDetermines intrinsic energy threshold Depends on “sea state” (surface agitation) cf. Wenz, J. Acoust.Soc. Am. 34 (1962) 1936

Ambient noise

Adapted fr. astro-ph/0104033 (Lehtinen et al.)‏

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Transient Background: Properties

~500

m

“qu

iet z

one”

em

issi

ons,

re

flect

ions

•  Very diverse�Shipping traffic, marine mammals, … �ð perform signal classification

•  Mostly originating from near surface�ð Impose cut based on source location

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•  For events selected by online filter, �reconstruct direction for individual storeys

•  When directions reconstructed by more than one storey get source location

Transient Background: Position Reconstruction

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Data: 156 days of measuring time �from Nov. 2009 to Oct. 2010

Source Localization

Problem: Small size of AMADEUS device �ð large errors in z, despite good angular � resolution for direction reconstruction:�

in zenith in azimuth

Solution: Project positions to sea surface and �remove event clusters from moving �sound emitters

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Δθ = 0.6± 0.2Δϕ =1.6± 0.2

Cluster Analysis of Moving Sound Emitting Objects

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x [m]

y [m

]

Nov. 2009

Oct. 2010

Signal Classification with Machine Learning Algorithms •  Different algorithms have been investigated:

•  Random Forest •  Boosted Trees •  Naïve Bayes •  Decision Tree •  Support Vector Machine

•  Recognition Error: •  For individual sensors < 10% •  For clusters of sensors < 2%

best performance

10

Dep

th z

[m]

Distance r [m]

-2500-2000-1500-1000

-500 0

500 1000

0 2000 4000 6000 8000 10000 1e-08

1e-07

1e-06

1e-05

0.0001

0.001

Even

t den

sity

[m-3

]

Spatial Distribution of Transient Background

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All clustered events

Dep

th z

[m]

Distance r [m]

-2500-2000-1500-1000

-500 0

500 1000

0 2000 4000 6000 8000 10000 1e-08

1e-07

1e-06

1e-05

0.0001

0.001

Even

t den

sity

[m-3

]

All reconstructed events 15·103 km−3 year−1

After signal classification and cluster analysis 100 km−3 year−1

Further Reduction of Transient Background

Search for characteristic geometry of pressure field from neutrino interaction (“pancake”) •  AMADEUS too small •  investigations with Monte Carlo simulations

(input from AMADEUS) •  KM3NeT: Combined system for acoustic

positioning and neutrino detection planned

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AMADEUS Effective Volume

13

Ve↵ =

Pp(E,x, ep)�sel

NgenVgen

Effective Volume

Number of Neutrinos: 107

Volume in which the Neutrinos are generated: 1200km3

Probability of the neutrino reaching the vertex

only counted if signal is detected;

Earth

ν

Water

10°

Earth density model (PREM)

AMADEUS Effective Volume

� Level 1:

•  low ambient noise •  minimal filter

Level 2: •  noise model •  std. filter

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10-5

10-4

10-3

10-2

10-1

100

101

9 9.5 10 10.5 11 11.5 12

V eff(

E) [k

m3 ]

E [log(E/Gev)]

Preliminary

Veff(Ei) Level 1Random Coincidences Level 1Veff(Ei) Level 2Random Coincidences Level 2

Preliminary

Conclusions and Outlook •  The AMADEUS system has all features of an

acoustic neutrino telescope (except size) •  Transient background: Strong suppression achieved,

further reduction much easier with larger (3D) detectors

•  Monte Carlo simulations developed and effective volume for AMADEUS derived

•  KM3NeT: Combined system for acoustic positioning and neutrino detection planned

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