Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS simulation…
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Transcript of Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS simulation…
Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTS
simulation…
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTS
Overview
simulation…
• Neutrino event generators
• Simulating UHE hadronic cascades
• (Fast) simulation of acoustic signal
• Large scale detector simulation
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTS
Neutrino interaction simulations
simulation…
• Aim: simulate the UHE neutrino interaction →y dependence
4simulation…Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSNeutrino interaction simulators
• You can assume a constant level of elasticity: Eh= 0.2 - 0.25 Eν e.g. SAUND, ACoRNE proposal
• Better if you produce a y distribution• Some neutrino interaction simulators exist that work at
UHEs– ANIS: All Neutrino Interaction Simulation, developed for
AMANDA (up to 1021eV)– PYTHIA: could be used to produce hadron energy fraction
(Bjorken y) of neutrino interaction…
5simulation…Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSNeutrino interaction simulators
RMS of ~27% of neutrino energy taken by hadron shower
n(NC) / n(CC) = 0.35
ANIS
6simulation…Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSNeutrino interaction simulators
PYTHIA vs. homemade (Terry Sloan)
Cross sectionMean Bjorken y
RMS Bjorken y
Okay up to 1021eV but pythia starts generating errors
7simulation…Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSNeutrino interaction simulators
Indications are that data agree well
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTS
Simulating UHE hadronic cascades
• Aim: to develop a robust method for simulating thermal energy densities from UHE hadronic cascades
simulation…
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSSimulating UHE hadronic Cascades•Current situation• There is no single, open source simulation
toolkit available for download that can simulate an UHE hadronic cascade in water.– Geant4 range of validity ends at 105GeV for
hadronic interactions– CORSIKA is good to 1021eV, but designed to
work above sea-level– Any other suitable candidates?...
simulation…
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSSimulating UHE hadronic Cascades
• Possible solution• GEANT4 + CORSIKA hybrid? • Modification of CORSIKA:
– Edit density functions such that interactions occur in water not air (1g/cm3)
– Turn off all atmospheric effects– Recompute cross-sections (maybe not if A dependence is
not too big)…• Work is underway to compare results of Geant4 and modified
CORSIKA at 105GeV, if they agree then CORSIKA will take over the UHE shower production
“What you are doing is not wrong” – Knapp, Heck
watch this space…simulation…
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSSimulating UHE hadronic Cascades
simulation…
• The shape of the acoustic signal is heavily dependent on the form of the thermal energy dependence– Current trend is to assume Gaussian cross-
section and Gamma function in longitudinal direction
– Indications are that this is not a fair assumption
• Once we are happy with thermal energy densities from GEANT, CORSIKA we can use DSP methods to produce a (more accurate) fit to the transverse energy distribution
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTS
Simulation of the acoustic signal
simulation…
• Aim: given a thermal energy density, compute the expected acoustic pressure pulse at an arbitrary location
13simulation…Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSSimulation of the acoustic signal• Two possible methods (described by S. Danaher)
– Standard method (ACorNE proposal, SAUND) …• Each MC point in thermal energy density is a
Gaussian integrate to generate acoustic signal• Very computer intensive: 5.11010 flops
– DSP method…• Each MC point is a delta function (the integral of
which is 1) convolve integrated deltas with Gaussian to retrieve signal
• Very fast ~ 104flops !
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTS
Large scale detector Simulation
• Aim: to make a prediction for the sensitivity* of the acoustic technique
*(so PPARC would give us our funding!)
simulation…
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSLarge scale detector Simulation• Method:
– simulate hadronic cascades up to 100TeV using Geant4• the range of validity of Geant4 physics extends only to
100TeV (105)GeV• we require thermal energy density of the hadronic shower to
calculate acoustic radiation…
simulation…
results are parameterised and extrapolated to UHE energies
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSLarge scale detector Simulation
• Method:– given a thermal energy density one can compute the
expected pressure pulse at some far-field location…– use the simulated acoustic pulses to find a simple
relationship between the neutrino energy and the peak pulse pressure (assume elasticity Eh = 0.25 Eν)
can now compute the expected peak pressure at a hydrophone location in a hypothetical array, however…
simulation…
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSLarge scale detector Simulation• Method:
– signal is modified by 3 factors of attenuation:• 1) geometric fall off of intensity
– intensity goes as 1/r2, pressure as 1/r
• 2) losses due to bulk water properties– fitted using a 4th order polynomial and coupled to
the output of a matched filter
• 3) angular spread – calculated using Fraunhoffer diffraction theory
simulation…
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
• Attenuation due to losses in a dense medium
simulation…
• Method:
behaviour of pulse with increasing distance
0.1 km 1 km
10 km 100 km
FUTURE PROSPECTSLarge scale detector Simulation
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSLarge scale detector Simulation
simulation…Angular Spread
• Method:
Pulse shapes at different angles in steps of 0.26
Time(s) 10-4
Re
lativ
e A
mp
litud
e
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSLarge scale detector Simulation
simulation…
•Method:•Coherent emission of radiation along shower axis confines signal to “pancake”
cut hydrophones greater than 5 out of plane of pancake ~ 100 times reduction in signal strength
• Pressure cut of 0.035Pa from threshold set by PFA (S. Danaher)
Far field Radiation pattern
Angle (degrees)
Pre
ssur
e (P
a)
100
10-3
-5 5
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSLarge scale detector Simulation
simulation…
•Method:•vertex reconstruction performed via the difference in arrival times of acoustic signal at hydrophones(SVD method, no refraction)
•various critical dimensions tried: inter-string, inter-storey, inter-”module”
•started with ANTARES style geometry…
•need to break regular symmetry for vertex reconstruction to work
only demand that vertex is reconstructed for sensitivity
calculation
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
Large scale detector Simulation
simulation…
Results – flux limit curve if no events are seen in 1 yr
FUTURE PROSPECTS• assuming we are only sensitive to hadronic shower
• threshold is limiting our sensitivity, improve with DSP, experimental experience?
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Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTSSimulation
simulation…
Prospects for the future…Many things still to consider, this is a
work in progress•Recalculate acoustic radiation using new simulation techniques
– Variation of pulse shapes due to cascade fluctuations
•Sound speed profiles– Refraction, (get a copy of Boyle!)...
•Pointing, energy reconstruction, array optimisations…– One day we will need a working full detector simulation
•Build an “Energy Simulator” to calibrate a hydrophone
24simulation…Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment
FUTURE PROSPECTS
END• Thanks for listening
• Any questions?