Simulating Hadronic Cascades
As
the
slide show
illustrates, the acoustic signal of a neutrino originates from the
heating effect of the particle cascade resulting from its collision
within a particular medium. This process has been studied
in detail
by the ACORNE
collaboration via Monte Carlo simulations using
the GEANT4
and CORSIKA programs.
A
parameterisation
of the cascades longitudinal and radial energy density, in water and
ice, has been determined.
Acoustic Pulse Calculations
Once the cascade energy density is known, the corresponding pressure differential at some other location can be calculated. This has been achieved with the additional feature of stochastic fluctuations in cascade profiles.
A Calibrated Source
It is desirable to have a calibrated acoustic source that can be used to emit neutrino-like pressure pulses for measurement by a suitable detector. A single omni-directional transducer has been characterised and subsequently driven to do this. The next step is to develop a linear array of transducers that produced a phased output which mimics the acoustic pancake produced by a UHE neutrino induced hadronic cascade.
The Rona Field Trip
The ACORNE collaboration utilises the QinetiQ Underwater Acoustic Range at Rona in the Northwest of Scotland. The acoustic calibrator was successfully deployed in the Inner Sound during September 2008.
Analysis of Rona Data
The ACORNE collaboration has in excess of 14TB of FLAC compressed audio data taken by the Rona hydrophones. A preliminary analysis of these data has been presented and is written about in a thesis.
Sensitivity Calculations
The ACORNE collaboration has also investigated the feasibility of kilometre scale arrays of hydrophones as UHE neutrino telescopes.
Summer Student Work
Nuffield funded Summer student Courtney Williams worked on the project during the summer of 2008. Courtney went on to present her work at The Big Bang UK Young Scientists and Engineers Fair where she was awarded the CREST EU Competition for Young Scientists' Prize.
Cascade Profile
2-dimensional profile of a hadronic cascade produced by GEANT4
simulation. For showers above 100 TeV a modified version of the
CORSIKA program is used to determine the energy deposition.
Maximum Pulse Height
Variation of the maximum pulse height as a function of distance
and angle from a 10¹¹ GeV primary.
Laboratory Based Development
Transducers are first tested in the ACORNE laboratory at The
University of Sheffield before being deployed in the field.
Deployment In The Field
A LabView Virtual Instrument was used to drive an omnidirectional
transducer with MATLAB generated waveforms above the QinetiQ
Acoustic Range at Rona
Diving for Neutrinos
A short duration, impulsive event in the data from Rona. Many
sources of 'noise' are present in the Inner Sound hpwever these
have been utilised as a sample data set in order to develop the
ACORNE data acquisition chain. Subsequent analysis of these
signals aims to discriminate between environmental, biological and
anthropogenic sources and neutrinos.
Sensitivity of km³ Hydrophone Arrays
The acoustic detection of UHE neutrinos can be competitive with
optical and radio based experiments but undoubtedly the best
performance will come from hybrid telescopes.
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