` Acoustic Detection Giorgio Riccobene INFN-LNS Giorgio Riccobene LNS
Motivations UHE neutrino fluxes Neutrino cross section at extreme enegy Giorgio Riccobene LNS
High Energy Neutrinos: What We (don’t) Know Optical Cherenkov Radio Radio and Acoustic Extending the neutrino observation to extreme energies astrophysics UHECR origin, GZK neutrinos cosmology decay of Plank scale massive particles, Topological Defects,… particle physics study neutrino cross section Giorgio Riccobene LNS
Large Area Detectors for HE neutrinos 1 TeV 100 PeV 1000 ZeV Acoustic Detection Radio Detection Optical Detection (Prototypes) (RICE, SALSA) (ICECUBE-KM3NeT) ν em cascade µ hadron ν µ cascade ν e em cascade Medium: Seawater, Polar Ice Medium: Seawater, Polar Ice, Medium: Salt domes, Polar Ice Salt Domes ν µ (throughgoing and contained) ν (cascades) ν e, τ (contained cascades) ν (cascades) Carrier: Cherenkov Radio Carrier: Cherenkov Light (UV-visible) Carrier: Sound waves (tens kHz) Attenuation length: 1 km Attenuation length: 100 m Attenuation length: ∼ 10 km Sensors: Antennas Sensor: PMTs Instrumented Volume: >1 km 3 Hydro(glacio)-phones Instrumented Volume: 1 km 3 Instrumented Volume: >100 km 3 Giorgio Riccobene LNS
A Short Summary of Activities on Acoustic Detection 1957 Askaryan Markov Zeleznyk 1979 Learned BNL, Harvard, SLAC - Beam Experiments ’80s DUMAND Kamchatcka ’90 SADCO 2000’s BAIKAL (ITEP, MSU, Irkutsk) ANTARES (Erlangen, Marseilles, Valencia) SAUND (Stanford, US Navy) ACORNE (Imperial College, Lancaster, Northumbria, Sheffield, UCL ) SPATS (DESY Zeuthen, Berkeley, Gent, Stockholm, Uppsala,…) NEMO (LNS, Roma, Pisa, Genova) Beam Experiment, Simulation, R&D, deep sea measurements thanks to neutrino telescopes’ infrastructures and military facilities after the end of cold war Giorgio Riccobene LNS
The Thermo-Acoustic Mechanism Basic Theory Beam Test Experiments Neutrino Acoustic Detection Giorgio Riccobene LNS
Basics of thermo-acoustics mechanism A pressure wave is generated instantaneous following a sudden deposition of energy in the medium (neglecting absorption: O(10 km) at 10 kHz ) Istantaneous deposition of heat through ionization -7 -8 t D / c 10 :10 sec ≈ ≈ deposition Thermo-acoustic process: increase of temperature (specific heat capacity C p ), expansion (expansion coeff β ) -5 � 10 sec >> t t ≈ expansion deposition ( ) .. ∂ ε r,t 1 β 2 ∇ p − p = − ⋅ 2 c c ∂ t s p For a point like source (micropulse): Learned r − t δ ∂ c E β Bipolar pulse s 0 ∝ p ( r , t ) spherical expansion ∂ 4 π c t r p For a shower heating a volume of matter (macropulse): Sum of pointlike sources: β ∂ 1 wavefront and signal shape p(r, t) ∝ ε dV ∂ ∫ depend on the energy density 4 π c t r p distribution Giorgio Riccobene LNS
Accelerator Experiments: results and open questions Recent measurements (2000’s) Brookhaven NL (Harvard, SLAC) 1979 Uppsala: 177 MeV p 200 MeV proton beam (LINAC) E= 10 16 – 10 17.5 eV Spill time 3 to 20 us Bipolar pulse observed Beam diameter 4.5 cm Energy deposited in water 10 19 � 10 21 eV Unclear dependence on temperature Other contibution to observed pulses ? Bipolar pulses observed Dependency on C p , T and on beam ITEP Synchrotron: 100, 200 MeV p diameter confirmed (about 10% E= 10 15 – 10 20 eV uncertainty) Measured pressure increses linearly with E Erlangen Laser Nd-YaG E= 10 17 – 10 19 eV Dependence on C p confirmed simulation reconstructed pulse Giorgio Riccobene LNS
Neutrino Acoustic Detection Principle � Neutrino Interaction (strong Earth absorption: look upward !) � Hadronic shower formation at interaction vertex ( ν e e.m. shower) neutrino � H shower carries (on average) ¼ E ν � Shower Development Weak interaction (LPM must be taken into account for EHE) � Sudden deposition of heat through ionization Hadronic shower � Thermo-acoustic process: Increase of temperature (C p ), Volume Expansion ( β ) The “pen shaped” energy deposition region (20 m depth, � 10 cm diameter) produces a pancake shaped acoustic ν e wave peak wavelength e.m.shower c s 10 kHz λ ≈ 2 d f = ≈ 2 d � Acoustic wave propagation in the 1 ( ) medium: near field p r ∝ max r Giorgio Riccobene LNS
Acoustic pulse amplitude in Salt, Water, and Ice Conversion of ionization energy into acoustic energy Med Sea S.P. ice NaCl T [ºC] 14º -51º 30º c s [m s -1 ] 1545 3920 4560 [ K -1 ] 25.5x10 -5 12.5x10 -5 11.6x10 -5 β [J kg -1 K -1 ] C P 3900 1720 839 2 β γ = c C 0.12:0.13 1.12 2.87 s p Gruneisen coefficient 1 Pa 21 − ≈ × × ≈ ⋅ p E 6 10 E γ in water max ν ν eV 4 Giorgio Riccobene LNS
The Size of Neutrino Acoustic Detectors E ν = 10 20 eV in water: p = 0.6 Pa @ 1 km � 20 mPa (neglecting attenuation) in Ice : p = 6 Pa @ 1 km � 200 mPa (neglecting attenuation) Underwater Cherenkov detectors Upgoing events – 100 TeV min eff 4 − P ( E ,E ) R N σ 10 = = CC A νµ ν µ µ N events D(N ) − σ ρ A Tot Earth P e Φ 2 π 100 = ≈ ν νµ 2 A T km y ⋅ eff WB flux Underwater Acoustic detectors Downgoing events – 10 20 eV eff 3 − P (E ,p ) H N 10 = σ ≈ det min det Tot A ν N events 3 − 10 ≈ 2 A T km y ⋅ eff Sound absorption length in ocean O(10 km), noise O(10 mPa) Several groups developing and improving simulation codes for large acoustic detectors What we can do with 1 km 3 filled with hydrophones ? Giorgio Riccobene LNS
Studies for a Future Large-Scale Acoustic Detector Study of Medium Properties Giorgio Riccobene LNS
Study of the Medium Acoustic Properties : Water Complex but well characterized by several military studies Absorption is mainly caused by chemical relaxation: B(OH) 3 50 Hz - 5 kHz MgSO 4 5 kHz – 500 kHz 2 π κ 8 2 a = 3 c f sound 3 ρ s L 10 km (at 10 kHz) ≈ a Sound velocity in water changes as a function of depth, tempeature and salinity at surface (T,S) dominated at large depth (increases linearly with pressure) ∆ c m/s 1545 c = s 1 65 cm/s/m = s . ∆ z � refraction pancake shape modification Giorgio Riccobene LNS
Acoustic Noise in Water Diffuse noise: Seismic, surface waves (wind), rain, thermal noise Impulsive noise: Cetaceans, man made shipping (also diffuse!) and instrumentation Man made noise is increasing (1 dB/year in densely inhabitated seas) tides, NEMO, SAUND, ANTARES seismic,… 5 kHz 50 kHz 2 years noise monitoring at 2000 m shipping NEMO-Test Site data (diffuse) sea state Measured Average noise Sea State 2 SS2 Sea State 0 SS0 thermal f [kHz] log 10 (f [kHz]) Knudsen’s Formula 5 3 / P( f ,SS ) 94 5 10 . log f 30 log( SS 1 ) = − + + Hz Giorgio Riccobene LNS
Study of the Medium Acoustic Properties : Polar Ice Not a well known medium…Need accurate in situ measurements ! scattering absorption speed of sound Rayleigh scattering molecular reorientation weak temperature at crystal � energy loss in dependence boundaries relaxation strong density dep. � crystal size temperature dependent � signal refraction � frequency crystal size dependent important in firn λ s ~a 3 × f 4 South Pole: pressure waves: theory: λ a (200m) = 8 km v s = 3900 m/s λ s (10 kHz) = 800 km λ a (2000m) = 0.8 km shear waves: λ s (100 kHz) = 0.2 km v s = 2000 m/s Absorption length / km measured in firn Depth/ m Depth/ m (J. Weihaupt) predicted in bulk ice Horizontal distance /m Depth/ km Longitudinal sound velocity m/s New results from SPATS Giorgio Riccobene LNS
Acoustic Noise in Ice Changes as a function of depth SPATS Measurements: Noise is stable Gaussian Independent on weather conditions No seasonal variation observed Absolute value determination is not possible now due to change of glaciophone sensitivity with pressure and temperature. Needs in situ calibration Giorgio Riccobene LNS
Studies for a Future Large-Scale Acoustic Detector Acoustic Neutrino Event Simulation Event Reconstruction Expected Effective Volume and Sensitivity Giorgio Riccobene LNS
Simulations of neutrino interaction and shower propagation Neutrino Interaction ANTARES(Erlangen,Marseilles) SAUND ACORNE -- Ghandi et al. Pythia ACORNE ANIS (from Amanda) ANIS .- HERWIG+CORSIKA neutrino shower simulator Shower development Similar results for CORSIKA Zheleznyk and Dedenko ν e 10 19 eV (e.m. shower including LPM) LPM SAUND LPM hadronic Alvarez Muniz-Zas ANTARES (Marseilles) hadronic GEANT 4 no LPM Hadronic + e.m. GEANT 4 +LPM Giorgio Riccobene LNS
Simulations of neutrino interaction and shower propagation Shower development ACORNE: CORSIKA modified for water transverse and longitudial energy deposits have been parameterized for fast simulations GEANT 4 fresh water GEANT 4 salt water CORSIKA Comparisons with GEANT: ~ 10% lower at peak Showers broader Comparison with NKG: less energy at smaller radii Astropart Phys V28 3 (2007) 366 low frequency contribution enhanced) Giorgio Riccobene LNS
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