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

1. FUTURE PROSPECTS simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

2. Overview FUTURE PROSPECTS • Neutrino event generators • Simulating UHE hadronic cascades • (Fast) simulation of acoustic signal • Large scale detector simulation simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

3. Neutrino interaction simulations FUTURE PROSPECTS • Aim: simulate the UHE neutrino interaction →y dependence simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

4. Neutrino interaction simulators FUTURE PROSPECTS • You can assume a constant level of elasticity: Eh= 0.2 - 0.25 Eνe.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… simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

5. Neutrino interaction simulators FUTURE PROSPECTS RMS of ~27% of neutrino energy taken by hadron shower n(NC) / n(CC) = 0.35 ANIS simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

6. Neutrino interaction simulators FUTURE PROSPECTS Mean Bjorken y Cross section RMS Bjorken y Okay up to 1021eV but pythia starts generating errors PYTHIA vs. homemade (Terry Sloan) simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

7. Neutrino interaction simulators FUTURE PROSPECTS Indications are that data agree well simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

8. Simulating UHE hadronic cascades FUTURE PROSPECTS • Aim: to develop a robust method for simulating thermal energy densities from UHE hadronic cascades simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

9. Simulating UHE hadronic Cascades FUTURE PROSPECTS • 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… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

10. Simulating UHE hadronic Cascades FUTURE PROSPECTS • 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… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

11. Simulating UHE hadronic Cascades FUTURE PROSPECTS • 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 simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

12. Simulation of the acoustic signal FUTURE PROSPECTS • Aim: given a thermal energy density, compute the expected acoustic pressure pulse at an arbitrary location simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

13. Simulation of the acoustic signal FUTURE PROSPECTS • 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: 5.11010 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 ! simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

14. Large scale detector Simulation FUTURE PROSPECTS • Aim: to make a prediction for the sensitivity* of the acoustic technique *(so PPARC would give us our funding!) simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

15. Large scale detector Simulation FUTURE PROSPECTS • 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… results are parameterised and extrapolated to UHE energies simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

16. Large scale detector Simulation FUTURE PROSPECTS • 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… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

17. Large scale detector Simulation FUTURE PROSPECTS • 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… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

18. Large scale detector Simulation FUTURE PROSPECTS • Attenuation due to losses in a dense medium Method: 0.1 km 1 km 10 km 100 km behaviour of pulse with increasing distance simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

19. Large scale detector Simulation FUTURE PROSPECTS Pulse shapes at different angles in steps of 0.26 Angular Spread Method: Relative Amplitude Time(s) 10-4 simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

20. Large scale detector Simulation FUTURE PROSPECTS Far field Radiation pattern 100 • 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 (Pa) Pressure cut of 0.035Pa from threshold set by PFA (S. Danaher) 10-3 -5 5 Angle (degrees) simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

21. Large scale detector Simulation FUTURE PROSPECTS • 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 simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

22. Large scale detector 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? simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

23. Simulation FUTURE PROSPECTS • 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 simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment

24. END FUTURE PROSPECTS • Thanks for listening • Any questions? simulation… Jonathan Perkin ARENA May 05AcousticCosmicRayNeutrinoExperiment