Acoustic Measurements in ANTARES: Status and Aims Robert Lahmann University Erlangen-Nuremberg June 28, 2006 ARENA 2006, Newcastle Outline: The ANTARES detector Acoustic detection of UHE neutrinos Acoustic detection with ANTARES Conclusion and Outlook

The ANTARES Collaboration IFIC, Valencia University of Catania LNS Catania University of Bari University of Rome University of Erlangen ITEP Moscow KVI Groningen NIKHEF, Amsterdam University of Bologna University of Pisa University of Genova IFREMER, Brest DSM/DAPNIA/CEA, Saclay APC Paris IPHC (IReS) Strasbourg Univ. de H.-A., Mulhouse CPPM, Marseille C.O.M. Marseille LAM, Marseille IFREMER, Toulon GeoAzur Villefranche Cable More than 20 Institutes from 6 European countries ANTARES 2500m depth aim: built and operate an neutrino telescope

The ANTARES Neutrino Telescope Hostile environment: Seafloor at 2500m depth (pressure up to 250 bar) sea water (corrosion) 12 detection lines with 25 storeys each Each line holds 75 PMTs

Basic detector element: storey Local Control Module (in the Ti-cylinder) Optical Module (OM): 17” glass sphere 10” PMT

ANTARES: Current Status Line 1, first complete line in operation since 2 March 2006 Mini Instrumentation Line with Optical Modules (MILOM) in operation since 12 April 2005 Production of remaining lines in progress 12 lines are expected to be operating by end 2007

) ANTARES is a Acoustics in ANTARES ANTARES = Astronomy with a Neutrino Telescope and Abyss environmental RESearch ) ANTARES is a water Cherenkov neutrino telescope and test platform for deep-sea investigations use the framework to evaluate the prospects of an acoustic neutrino detector and test acoustic neutrino detection methods

Acoustic Signature of UHE Showers Askaryan, 1979 10PeV@400m Energy deposition Water gets heated (nK) expansion pressure pulse A.V. Butkevich et al., Phys. Part. Nuc., 29 (3), 266, 1998 Advantage: acoustic absorption length ~ km !!!

Acoustic Background BIP Correlated BIP rate ) main objective! General background contributions: inherent noise of sensor/electronics thermal noise of water noise from sea surface point sources.... 2P Important background: Bipolar Pressure Signal BIP From individual hydrophones: single BIP rate; From several hydrophones: Correlated BIP rate ) main objective!

ANTARES: Setup with Acoustics 3 more Acoustic Storeys in an additional line: Plans to be finalized Instrumentation Line with 3 Acoustic storeys Deployment foreseen first half 2007

Integration of acoustics into the IL Plan: Install 3 acoustic storeys in the Instrumentation Line for 2007 deployment in a depth of ~2300m to ~2180m Strategy: Use unmodified ANTARES components (mechanical, electronic) wherever possible Use mainly commercial parts for additional electronics, cables, connectors (Details in the presentation of Kay Graf tomorrow) ~14.5m ~100m

Arrangement of Sensors ~1m : - local coincidences for suppression of uncorrelated background hydrophones 15m to 100m : - directional reconstruction Aim: measurement of BIP-event density in a large volume (km3) for a long time (yr) with a dedicated array of acoustic sensors

Measurements with one storey Coincidence trigger from k out of N hydrophones: Look for correlated signal shapes above a threshold within a time window (T~1ms): ~1m 0 ms 0.1 ms 0.2 ms 0.3 ms 0.4 ms 0.5 ms 0.6 ms 0.7 ms t [s] Can also perform reconstruction of direction/ distance (with limited accuracy)

Investigations with one line Acoustic sensors along one line: Focus on random coincidences and coherence length How do random coincidences compare to rates from point sources at different length scales? Coherence length: How do signal shapes correlate along a wave front? Point sources

Autonomous Transponders Position Reconstruction of Storeys Acoustic reconstruction in ANTARES: Transceivers: Sender/Receiver on Bottom String Socket (BSS) of MILOM (plus Line 1 and future detection lines) Autonomous Transponders Benefit for acoustic detection: As for optical track reconstruction: know position of acoustic storeys to better than 10 cm Transmitters can be used for calibration MILOM BSS 226m 175m Autonomous Transponders In addition: orientation of each storey has to be reconstructed: Compass, tiltmeter in every storey (inside electronics container)

Setup of a 3D-array 1km3 volume MC-Investigations by T. Karg (Ph.D. thesis & ARENA05): Number of “Acoustic Clusters” (ACs, e.g. ANTARES acoustic storeys) in a 1km3 cube 400 AC 200 AC 50 AC 10 AC 800 AC 1km3 volume Sensor threshold 5mPa (SS0: RMS ~2.5mPa integrated from 1kHz to 100kHz): No significant change above 200 AMs/km3

BIP - Measurements ~200m ~115m 200 ACs/km3 corresponds to inter-AC distance of ~170m → excellent opportunity for realistic 3-dim reconstruction with ANTARES when a second line is equipped with acoustic sensors: ~200m ~115m

Conclusions and Outlook Currently two lines in operation at ANTARES site The ANTARES detector poses an excellent opportunity to study acoustic detection methods First acoustic components for investigation of acoustic background to be installed in first half of 2007 All 12 detection lines expected to be deployed and connected by end 2007 Acoustic equipment on an additional line foreseen