Jonathan Perkin SUD Catania 07 Acoustic Cosmic Ray Neutrino Experiment Status report 2007… Status...

Jonathan Perkin SUD Catania 07 Acoustic Cosmic Ray Neutrino Experiment

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Status report

2007…


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Introduction: ACoRNE collaboration institutions

• The Acoustic Cosmic Ray Neutrino Experiment is a UK collaboration represented by researchers at:– Imperial College London– The University of Lancaster– The University of Northumbria– The University of Sheffield (Coordinator - Lee Thompson)

– University College London

• The project is funded through JGS by PPARC and DSTL and allows us access to QinetiQ acoustic range off Rona in NW Scotland.


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• Data Acquisition– Rona acoustic range– ACoRNE DAQ philosophy– ACoRNE filter chain

• Hardware Development– Calibration devices

• Signal Processing and Data Analysis– Rona DAQ– Offline filtering and analysis

• MC simulations– Hadronic shower simulations– Large scale future detectors and hybrid arrays

Contents: ACoRNE key skills / deliverables


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The Rona underwater acoustic range• Comprises 8 wideband

hydrophones: ITC-8201 flat -158 dB/v/µPa from 0.01-65kHz, omnidirectional

• Distributed around a rectangle ~1200m x 200m at mid depth in 230m deep water

• Readout is 16Bit @ 140kHz• Rona has a facility to locate

hydrophone positions via acoustic beacons but this is offline when we take data

MOVIE


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ACoRNE DAQ philosophy

• All data to shore - unfiltered• All processing and analysis offline• 8TB RAID interfacing to LT03 tape robot (400GB/tape) with

16 tape autoloader and barcode reader– This DAQ system is under the ownership of the ACoRNE

collaboration and in essence can move to another location should the opportunity arise

• FLAC lossless codec providing ~55% compression on WAV audio files

• Linear phase filtering enabled• Unlimited ability to reprocess raw data• Filters evolving over time


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ACoRNE filter chain

• Currently, raw data is passed through reduction process encompassing a series of filters designed to optimise retention of neutrino-like signals

• 4 types of trigger in order of increasing priority– T1 = P– T2 = dP/dT– T3 = d2P/dT2

– T4 = M, where M is one or more matched filters

• Data analysed in 10s intervals• Top 5 of each trigger per interval saved

– 1000 samples either side of trigger + time stamp + type


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ACoRNE filter chain

• Now on second generation of filters…– 1st generation used single matched filter which was

optimised for bipolar acoustic pulses at 1km from range, in the plane of the acoustic pancake

– 2nd generation uses 9 matched filters optimised for varying distance up to 2.5km from centre of range and ±2.5° out of the pancake plane

• Given the dimensions and angular acceptance of the array to pancake like emission can optimise for distances and angles detectable neutrinos are most likely to inhabit


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Rona data

• First campaign 9th-24th December 2005 ~2.8TB raw data (@~55% compression) 1 matched filter in reduction– 12.453x106 ‘events’ retained after passing through

reduction – Novel analysis performed, requiring: >= 4fold coincidence

above 35mPa threshold– Events categorised in terms of Fourier spectra

• Second campaign in progress, currently amassed ~15TB (@~55% compression)– Analysis underway, following further development of

matched filter


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Hardware development: calibration devices

• Hence generating acoustic pancake from thermoacoustic emission

• High power (>1J per <100µs pulse) lasers could facilitate this requirement, availability and deployment are limiting factors…

• Meaningful astronomy via the acoustic detection of UHE neutrinos relies on our ability to calibrate hydrophones

• The perfect calibration tool would deposit thermal energy in the sea with equivalent dimension and density to a neutrino induced hadronic cascade


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• An equivalent signal to that produced by the thermacoustic mechanism can be produced via acoustic transducers

• First stage in this process is to generate a bipolar acoustic pulse from a single, omnidirectional element

• Next step involves a linear array of transducers emitting in phase to create an interference pattern analogous to the acoustic pancake resulting from a hadronic cascade in the sea

• More on this in calibration talk….


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• This summer the ACoRNE collaboration will deploy an omnidirectional, single element calibration source above the Rona acoustic range

• For the first time we will be able to test the emission and detection of a neutrino-like bipolar acoustic pulse in situ and in the presence of noise

• Thus far tests have been performed in the ACoRNE tank, the Sheffield University swimming pool, and, Kelk lake (East Yorkshire)…


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Signal processing and data analysis

• A novel analysis of the first 2.8TB of Rona data from the first campaign was undertaken (J.Perkin thesis)

• Simple coincidence and threshold cuts, in accordance with large scale detector simulation (discussed later) and analysis of Fourier spectra were used to classify different types of recurring event in the data– Threshold 35mPa– Coincidence >= 4 hydrophones– Coincident signals were required to show same features in DFT

spectrum

• 3526 of the 12.453x106 reduced events met passed cuts


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Some classes of ‘event’ observed at Rona

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.





~50kHz oscillating signal


Short-lived impulsive event

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Sample No.

140kHz sample rateN=27=128 sample FFT


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Some classes of ‘event’ observed at Rona







A ‘bipolar’ event

A ‘ringing’ event


Pre

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Sample No.

140kHz sample rateN=27=128 sample FFT


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Offline filtering and analysis: Matched triggers

• The matched trigger will try to pattern match the pulse shape

• It is optimised to Knudsen Noise

• Plotted here is the derivative of ~1000 triggers and the derivative of our expected bipolar pulse

• Note time delay of filter causes the pulse maximum to be at ~ -70µs


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Offline filtering and analysis: variation of triggered events with time

Day in Dec 2005

Nor

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No obvious correlation with time


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Offline Analysis• 13 dimensional phase space to explore:

– Pulse Width– Pulse Periodicity– Relative Energy– Pulse Multiplicity– Dominant Frequency– Sinusoidalness– Bipolarity– Standard Deviation– Skewness– Kurtosis (Gaussianisity)– Assymetry of Standard Deviation– Assymetry of Skewness– Assymetry of Kurtosis

• Prioritisation/optimisation of phase space parameters is underway….


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Monte Carlo Simulations: hadronic cascades in seawater (and ice)

• Paper submitted to Astroparticle Physics [arXiv:0704.1025]

• Developed an extension to the CORSIKA air shower program enabling the simulation of UHE neutrino induced hadronic cascades in water and/or ice

• Validated via comparison with Geant4 (E<100TeV) and then compared with existing parameterisations (~NKG, Niess & Bertin)

• Parameterisation of modified CORSIKA results proposed to allow for fast computation of thermal energy density - for use in large-scale detector simulations


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QuickTime™ and aTIFF (Uncompressed) decompressor


Modified CORSIKA: verifying LPM effect

• Firstly: varify LPM effect is implemented in CORSIKA

• Suppresses PP and Brems in EM showers

• Only energy density of hadronic part of interaction sufficient for thermoacoustic emission


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CORSIKA vs Geant4 at 1-100TeV• Next verify that modified

version of CORSIKA agrees with Geant4 to validate modifications made to CORSIKA

• Agreement within 20-30% accuracy of calculated neutrino-nucleon cross sections / physics models






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Modified CORSIKA: from proton induced showers to neutrino induced showers

• The thermal energy density resultant from a single high energy proton is ~ the same as that resulting from a UHE neutrino interaction multiplied by a scale factor


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The acoustic pulse from a CORSIKA generated shower

• The acoustic signal 1km from shower axis in the pancake plane

• Average of 100 CORSIKA showers at 109 GeV in water

• The curves show the deposited energies within cores of radius 1.025g cm2, 2.05g cm2 and the whole shower respectively

• It can be seen that most of the amplitude comes from the energy within a core of radius 2.05g cm2


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Comparison of CORSIKA with existing parameterisations

Good agreement with Niess & Bertin (within model uncertainties)


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Conclusions from CORSIKA study

• The thermoacoustic energy deposited by UHE neutrino induced hadronic cascades can be simulated in seawater and ice without extrapolating results from lower energy physics toolkits such as Geant4

• The acoustic signal generated by a hadronic cascade is very sensitive to the core of the shower

• Hadronic cascades initiated by protons and neutrinos are broadly equivalent if one scales for the energy transfer from the neutrino to the hadronic component of the event

• A parameterisation of the CORSIKA results to be used for fast computation of thermoacoustic energy densities has been proposed - a combination of modified versions of the Gaisser-Hillas (longitudinal) and NKG (radial) functions are used [see paper for definition]


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MC simulations: estimating the sensitivity of large-scale hydrophone arrays to the flux of UHE neutrinos

• A simulation toolkit based in C++/ROOT has been constructed to facilitate estimations of the performance of large-scale underwater arrays of hydrophones

• The program executes the following steps:– An ensemble of downward going neutrinos is generated, with an

energy spectrum flat in LogE– A hydrophone array is ‘constructed’ in a deep sea environment from a

file containing the coordinates of typically 1000 hydrophones distributed at random in 1km3

– The program then samples the neutrino spectrum on an event by event basis

• Each neutrino is forced to interact in a fiducial volume called the can surrounding the hydrophones

• Those hydrophones that do not intersect with the acoustic pancake are cut


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Sensitivity of large scale hydrophone arrays…

• The peak pressure as a function of neutrino energy and attenuation at each remaining hydrophone is calculated for both refracted and unrefracted sound rays, assuming each detector has an omnidirectional sensitivity

• The pressure amplitude and arrival time for all those hydrophones that register a signal above threshold is recorded, taking into consideration the matched filter performance

– For those events that register hits above threshold reconstruction of the interaction vertex and neutrino trajectory is attempted

– If the vertex reconstruction algorithm returns an unphysical vertex the event is discarded, otherwise it classified as a detection

– The sensitivity of the hydrophone array under examination is calculated from the number of reconstructed events. This is translated into a limit on the neutrino flux assuming that the hydrophone array detected no events for a given period of observation.


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Sensitivity of large scale hydrophone arrays…

• We want to be able to detect GZK neutrinos, therefore we have to think big!– 1500km3, 100hydros/km3 5yrs, 5mPa threshold


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Simulation of hybrid arrays…

• Within the KM3NeT collaboration a Mathematica based simulation toolkit has been developed for (fast) calculation of optical neutrino telescope performance - NESSY

• NESSY is further optimised for calculation of detector cost as well as physics capability

• The ACoRNE collaboration aims to further develop the NESSY program to include acoustic detection and thus enable the simulation of hybrid arrays


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Summary of ACoRNE activities• Over 17TB of data are on tape from the Rona acoustic range, new set of

offline filters integrated into analysis

• Omnidirectional bipolar calibration source ready to deploy in sea above Rona range, vessel for sea operations is chartered, awaiting confirmation from QinetiQ

• A new parameterisation based on results from a modified version of the CORSIKA program to enable fast computation of thermal energy densities resulting from neutrino interactions in water and ice has been realised

• An existing code is available for the simulation of large scale hydrophone arrays

• Work is underway to include the acoustic technique in a new Mathematica based program for fast simulation of hybrid detectors


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Future plans for ACoRNE

• Combine noise data from Rona with MET office data and perform coincidence study

• Continue analysis and evolution of offline filtering to maximise signal/noise

• Deploy omnidirectional bipolar source in sea over Rona range and verify detection capability

• Upgrade omnidirectional calibrator to linear phased array and put a pancake-like signal in the sea (Ensure this technology is good for ~2km depth and deployment at alternative sites e.g. Nemo test site, Capo Passero)

• Complete upgrade to KM3NeT Mathematica code for simulation of hybrid detectors

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Jonathan Perkin SUD Catania 07 Acoustic Cosmic Ray Neutrino Experiment Status report 2007… Status...

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