Jonathan Perkin ARENA May 05 A coustic Co smic R ay N eutrino E xperiment

Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment

FUTURE PROSPECTS

simulation…

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FUTURE PROSPECTS

Overview

simulation…

• Neutrino event generators

• Simulating UHE hadronic cascades

• (Fast) simulation of acoustic signal

• Large scale detector simulation

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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…



RMS of ~27% of neutrino energy taken by hadron shower

n(NC) / n(CC) = 0.35

ANIS



PYTHIA vs. homemade (Terry Sloan)

Cross sectionMean Bjorken y

RMS Bjorken y

Okay up to 1021eV but pythia starts generating errors



Indications are that data agree well

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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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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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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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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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FUTURE PROSPECTS

Simulation of the acoustic signal

simulation…

• Aim: given a thermal energy density, compute the expected acoustic pressure pulse at an arbitrary location


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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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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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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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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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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• 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


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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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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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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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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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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


FUTURE PROSPECTS

END• Thanks for listening

• Any questions?

Jonathan Perkin ARENA May 05 A coustic Co smic R ay N eutrino E xperiment

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