1. Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS simulation…

2. 2 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

3. 3 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Neutrino interaction simulations simulation… Aim: simulate the UHE neutrino interaction →y dependence

4. 4 simulation… Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Neutrino interaction simulators You can assume a constant level of elasticity: E h = 0.2 - 0.25 E ν 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 10 21 eV) –PYTHIA: could be used to produce hadron energy fraction (Bjorken y) of neutrino interaction…

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

6. 6 simulation… Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Neutrino interaction simulators PYTHIA vs. homemade (Terry Sloan) Cross sectionMean Bjorken y RMS Bjorken y Okay up to 10 21 eV but pythia starts generating errors

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

8. 8 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…

9. 9 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Simulating 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 10 5 GeV for hadronic interactions –CORSIKA is good to 10 21 eV, but designed to work above sea-level –Any other suitable candidates?... simulation…

10. 10 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Simulating UHE hadronic Cascades Possible solution GEANT4 + CORSIKA hybrid? Modification of CORSIKA: –Edit density functions such that interactions occur in water not air (1g/cm 3 ) –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 10 5 GeV, 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…

11. 11 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Simulating 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

12. 12 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

13. 13 simulation… Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Simulation 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: 5.1  10 10 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 ~ 10 4 flops !

14. 14 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…

15. 15 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Large scale detector Simulation Method: –simulate hadronic cascades up to 100TeV using Geant4 the range of validity of Geant4 physics extends only to 100TeV (10 5 )GeV we require thermal energy density of the hadronic shower to calculate acoustic radiation… simulation… results are parameterised and extrapolated to UHE energies

16. 16 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Large 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 E h = 0.25 E ν ) can now compute the expected peak pressure at a hydrophone location in a hypothetical array, however… simulation…

17. 17 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Large scale detector Simulation Method: –signal is modified by 3 factors of attenuation: 1) geometric fall off of intensity –intensity goes as 1/r 2, pressure as 1/r 2) losses due to bulk water properties –fitted using a 4 th order polynomial and coupled to the output of a matched filter 3) angular spread –calculated using Fraunhoffer diffraction theory simulation…

18. 18 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 km1 km 10 km100 km FUTURE PROSPECTS Large scale detector Simulation

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

20. 20 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Large 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) Pressure (Pa) 10 0 10 -3 -5 5

21. 21 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Large 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

22. 22 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?

23. 23 Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS Simulation 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

24. 24 simulation… Jonathan Perkin ARENA May 05 Acoustic Cosmic Ray Neutrino Experiment FUTURE PROSPECTS END Thanks for listening Any questions?