1 / 16

Acoustic Signal Computations in the Mediterranean Sea

Acoustic Signal Computations in the Mediterranean Sea. ARENA 2006, Newcastle V. Bertin, V. Niess CPPM - IN2P3/CNRS - U. Méditerranée – France. General Context. Dedicated Acoustic ‘team’ at CPPM ( 2002-2005 ) With Engineers & Physicists, mostly involved in ANTARES.

kylynn-jones
Download Presentation

Acoustic Signal Computations in the Mediterranean Sea

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Acoustic Signal Computations in the Mediterranean Sea ARENA 2006, Newcastle V. Bertin, V. Niess CPPM - IN2P3/CNRS - U. Méditerranée – France V. Bertin, V. Niess- ARENA 2006 - Newcastle

  2. General Context Dedicated Acoustic ‘team’ at CPPM ( 2002-2005 ) With Engineers & Physicists, mostly involved in ANTARES • PhD work at CPPM ( September 2002-September 2005 ) • See i.e. : • Stanford Workshop 2003 • ICRC 2005, Pune http://marwww.in2p3.fr/~niess/these.pdf (in French) astro-ph/0511617 ( to be published in Astroparticle Physics ) This Presentation Focuses on Acoustic Signal Computations V. Bertin, V. Niess- ARENA 2006 - Newcastle

  3. A Brief Reminding Thermo-acoustic coupling mechanism ( Askaryian, 1957 ; Sulak et al., 1978 ) 3) Output : Pressure signal ( Transduction … ) 1) Input : Energy density ( UHE Particle showers ) 2) Propagation : Vertically stratified medium ( Refraction ) Thermodynamic factor Constant here ( Mediterranean Sea, 1 km depth ) V. Bertin, V. Niess- ARENA 2006 - Newcastle

  4. Modelling Energy Deposition • Thermo-Acoustic emission : • Efficiency increases with energy density • Showers required Deep Inelastic Scattering Cross sections from : Gandhi et al. Phys. Rev. D58, 093009 (1998) Considering : J. Alvarez-Muniz, E. Zas Phys. Lett. B 441 (1997) 218 Phys. Lett. B 434 (1998) 396 n n, l W,Z • Focus on 2 limit cases : • necharged current ( CC ) : • because 100 % of ne energy goes into showers • but strong LPM spread … •  dedicated Monte carlo • nLneutral current ( NC ) : • because it is presumed giving compact showers • but only ~20 % of the nL energy •  Parametrisation ( GEANT 4/ EAS data ) hadrons N hadrons hadronic and electromagnetic showers V. Bertin, V. Niess- ARENA 2006 - Newcastle

  5. GEANT4 : Longitudinal Profile Extensive Air Showers, from M. Nagano and A. Watson Rev. Mod. Phys., Vol 72, No. 3, July 2000 ‘PDG Parameterisation’ : Good agreement GEANT 4, QGSP In a water box LPM ?? Depth of maximum ( g/cm2 ) Depth of maximum ( X0 ) ELPM Geant 4, p GEANT 4 results are consistent with Extensive Air Showers But LPM is a Matter effect … V. Bertin, V. Niess- ARENA 2006 - Newcastle

  6. GEANT 4 : Lateral Distribution Power law behaviour Sustained by Microscopic observation of ~ 100 GeV e-showers in Lead plate/Emulsion N. Hotta et al. Phys. Rev. D, Vol 22, No. 1, July 1980 GEANT 4 E  50 TeV Lateral exponents Core exponent ( ~10 % agreement with EAS) r/rm z/zmax Exponents varymostly with depth little with primary nature and energy ( @ 50+ TeV ) 5·10-4 rm V. Bertin, V. Niess- ARENA 2006 - Newcastle

  7. Electromagnetic LPM : Scheme • Use a dedicated 2 steps scheme : • Randomize the high energy part of shower ( LPM fluctuations ) • Reconstruct : Filter with average parametrisations for secondary showers primary Monte-Carlo (Metropolis) 1D 2D (FIR algorithms) Migdal’s cross sections for LPM : Not constrained experimentally in the strong suppression regime we are concerned with V. Bertin, V. Niess- ARENA 2006 - Newcastle

  8. Electromagnetic LPM : Results LPM ‘tail’ hadronic g( 5·1013 eV ) ne ( 1019 eV ) Parametrisation extends up to 1017 eV Longitudinal profiles of energy deposition Depth of the maximum LPM cascades stochastic LPM zmax ( X0 ) Normalised longitudinal density GEANT4 log10( E / 1 GeV ) Depth [ z ] (m) V. Bertin, V. Niess- ARENA 2006 - Newcastle

  9. Acoustic Signal Computation • Approximate Green function : No (de)-focusing ( ~ few % ) Propagation time : Ray tracing model Strength of signal = time/spatial coherence : This is where to play … • Reduce integral to 1D with causality/symmetries : Sum over 2 acoustic rays Transform of lateral distribution Observer point, Time & Ray structure Longitudinaldensity V. Bertin, V. Niess- ARENA 2006 - Newcastle

  10. Propagation Loss Signal Strongly modelled by Absorption Phase dependent model Driven by : L. Liebermann Phys. Rev. 76(10), November 1949 With ‘modern’ input from : R.E. Francois and G.R. Garrison J. Acoust. Soc.Am. 72(6), 1982 Viscosity 1/f2 Impulse response ( scaled ) Absorption length ( km ) B(OH)3 Transition from MgSO4 Delayed Impulse response MgSO4 Time ( scaled ) Frequency ( kHz ) V. Bertin, V. Niess- ARENA 2006 - Newcastle

  11. Near Field/ Far Field Pressure field ( mPa ) ne CC, En = 125 EeV, 10 km distance Transition : Cylindrical wave-front ( near field ) Angular aperture ( NC compact cascades ) LPM Fuzzy image Longitudinal density Compact cascades : Rigorous far field conditions achieved only at ~10 km Spherical wave-front ( far field ) V. Bertin, V. Niess- ARENA 2006 - Newcastle

  12. Signal Shape R/C versus Dt diagram • Signal characterised by : • Duration : Dt • Symmetry ratio : R/C Signal more asymmetric than previous studies Get insight on source nature, extension ( R/C ), distance ( Dt ) V. Bertin, V. Niess- ARENA 2006 - Newcastle

  13. Mediterranean Sea Refraction Mediterranean Sea Linear sound velocity profile Below 100 m Pressure field ( mPa ) @ 1 km from the source Global deflection given by a ray tracing model z ( m ) z ( m ) q Directivity only depends on q Deflection q Amplitude is little affected Effect is mostly native : Local sound velocity variation on energy deposition area Not ray structure Amplitude ( mPa ) Time ( ms ) V. Bertin, V. Niess- ARENA 2006 - Newcastle

  14. Effective Volume Signal threshold levels : 1 to 10 mPa Energies : 1018 to 1020 eV Model driven extrapolation 1 km 1 km3 Near field, CC ne Sonic Volume ( dB ref 1 km3 ) Signal amplitude ( dB ref 1 mPa ) Far field, NC nL Model Parameters : Range rmax, Effective length Leff, effective angular aperture Dqeff Amplitude ( dB ref 1 mPa ) Range ( dB ref 1 m ) V. Bertin, V. Niess- ARENA 2006 - Newcastle

  15. Boundary effects Water extension is vertically limited Shadowing from the sea bed ( Refraction ) zi = H/2 Source Hypothesis : Direct detection At long range Detection limited Close to vertical cascades Shadow Zone Shadow Factor : Efficiency = 1 - F Mean geometric efficiency ( % ) Pure Monte-Carlo Analytical & Monte-Carlo H = 2500 m depth Receiver zi =448 m above sea bed rmax/( H/2 ) V. Bertin, V. Niess- ARENA 2006 - Newcastle

  16. Benchmark Sensitivity Estimates 1018 eV 1020 eV Sea Noise 1-10 mPa in B = 100 khz ( Ceramic eq. ~ 2-6 mPa ) 1 evt/decade/year 1/E2 Flux  1 an E2f~10-6 GeV·cm-2· sr-1· s-1 Flattening due to boundaries Mediterranean Sea 2500 m depth (ANTARES like) V. Bertin, V. Niess- ARENA 2006 - Newcastle

More Related