27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 1

Acoustic Signal Computations in Acoustic Signal Computations in the Mediterranean Seathe Mediterranean Sea

ARENA 2006, NewcastleARENA 2006, Newcastle

V. Bertin, V. NiessCPPM - IN2P3/CNRS - U. Méditerranée – France

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 2

General ContextGeneral Context

This Presentation Focuses on Acoustic Signal Computations

•PhD work at CPPM ( PhD work at CPPM ( September 2002-September 2002-September 2005 )September 2005 )

Dedicated Acoustic ‘team’ Dedicated Acoustic ‘team’ at CPPM ( 2002-2005 )at CPPM ( 2002-2005 )With Engineers & With Engineers & Physicists, mostly Physicists, mostly involved in involved in ANTARESANTARES

See i.e. :See i.e. :•Stanford Workshop 2003Stanford Workshop 2003•ICRC 2005, PuneICRC 2005, Punehttp://marwww.in2p3.fr/~niess/these.pdf (in French)

astro-ph/0511617 ( to be published in Astroparticle Physics )

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 3

A Brief RemindingA Brief Reminding

2

2

2

2

2

1)

1(

t

q

Ct

p

cp

ps

Thermo-acoustic coupling mechanism ( Askaryian, 1957 ; Sulak et al., 1978 )

2) Propagation :Vertically stratified medium( Refraction )

3) Output :Pressure signal( Transduction … )

1) Input :Energy density( UHE Particle showers )

Thermodynamic factorConstant here

( Mediterranean Sea, 1 km depth )

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 4

Modelling Energy DepositionModelling Energy Deposition

Cross sections from :Gandhi et al.Phys. Rev. D58, 093009 (1998)

hadronic and electromagnetic showers

N

, l

W,Z

hadrons

Deep Inelastic Scattering

hadrons

•Thermo-Acoustic emission :Efficiency increases with energy densityShowers required

Focus on 2 limit cases :• e charged current ( CC ) : because 100 % of e energy goes into showersbut strong LPM spread … dedicated Monte carlo• L neutral current ( NC ) : because it is presumed giving compact showersbut only ~20 % of the L energy Parametrisation ( GEANT 4/ EAS data )

Considering :J. Alvarez-Muniz, E. ZasPhys. Lett. B 441 (1997) 218Phys. Lett. B 434 (1998) 396

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 5

GEANT4 : Longitudinal ProfileGEANT4 : Longitudinal Profile

GEANT 4, QGSPIn a water box

Extensive Air Showers, fromM. Nagano and A. Watson

Rev. Mod. Phys., Vol 72, No. 3, July 2000

Geant 4,

GEANT 4 results are consistent with Extensive Air ShowersBut LPM is a Matter effect …

Dep

th o

f m

axim

um (

X0 )

Dep

th o

f m

axim

um (

g/c

m2 )

LPM ??

ELPM

)(

)exp()()(

1

0

0

0 a

btbtb

X

E

X

ztf

a

z

‘PDG Parameterisation’ : Good agreement

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 6

GEANT 4 : Lateral DistributionGEANT 4 : Lateral Distribution

Sustained byMicroscopic observation of

~ 100 GeV e-showers in Lead plate/EmulsionN. Hotta et al.

Phys. Rev. D, Vol 22, No. 1, July 1980

Power law behaviour

5·10-4 rm

GEANT 4

Exponents vary mostly with depthlittle with primary nature and energy

( @ 50+ TeV )

Core exponent ( ~10 % agreement with EAS)

z/zmax

Lat

eral

exp

onen

ts

E 50 TeV

/rm

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 7

Electromagnetic LPM : SchemeElectromagnetic LPM : Scheme

1D

2D

Use a dedicated 2 steps scheme :1. Randomize the high energy part of shower ( LPM fluctuations )2. Reconstruct : Filter with average parametrisations for secondary showers

Monte-Carlo(Metropolis)

(FIR algorithms)

primary

Migdal’s cross sections for LPM : Not constrained experimentally in the strong suppression regime we are concerned with

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 8

Electromagnetic LPM : ResultsElectromagnetic LPM : Results

Parametrisation extends up to 1017 eV

LPMLPM cascades

stochastic

5.0, EL

Longitudinal profiles of energy depositionDepth of the maximum

log10( E / 1 GeV )

z max

( X

0 )

Nor

ma l

ised

long

itu d

inal

de n

s ity

Depth [ z ] (m)

GEANT4

e ( 1019 eV )

LPM ‘tail’

hadronic ( 5·1013 eV )

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 9

Acoustic Signal ComputationAcoustic Signal Computation

')'('

))',((

4),( 3rdrq

rr

rrt

tCtrp

p

2

1

2/

0

0 ),()(4

),,(i

izizp

dzGzftC

tzp

Propagation time :Ray tracing model

•Approximate Green function : No (de)-focusing ( ~ few % )

Strength of signal = time/spatial coherence : This is where to play …

•Reduce integral to 1D with causality/symmetries :

Sum over 2 acoustic rays

Longitudinal density

Transform of lateral distribution

Observer point, Time & Ray structure

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 10

Propagation LossPropagation LossSignal Strongly modelled by Absorption

Phase dependent modelDriven by :L. LiebermannPhys. Rev. 76(10), November 1949With ‘modern’ input from :R.E. Francois and G.R. GarrisonJ. Acoust. Soc.Am. 72(6), 1982

Ab

sorp

t ion

l en

gth

( k

m )

Imp

uls

e re

spon

se (

sca

led

)

Frequency ( kHz ) Time ( scaled )

MgSO4

B(OH)3

Viscosity1/f2

Transition from MgSO4

Delayed Impulse response

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 11

Near Field/ Far FieldNear Field/ Far Field

Angular aperture( NC compact cascades )

Pressure field ( mPa )e CC, E = 125 EeV, 10 km distance

LPM

Spherical wave-front( far field )

Fuzzy image Longitudinal density

Cylindrical wave-front( near field )

Compact cascades :Rigorous far field conditions

achieved only at ~10 km

km]100;5.0[2

2*

L

rTransition :

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 12

Signal ShapeSignal ShapeR/C versus t diagram

Signal characterised by :•Duration : t•Symmetry ratio : R/C

Get insight on source nature, extension ( R/C ), distance ( t )

Signal more asymmetric than previous studies

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 13

Mediterranean Sea RefractionMediterranean Sea RefractionMediterranean Sea

Linear sound velocity profileBelow 100 m

cm/s/m65.1

z

ck s

c

z (

m )

z (

m )

Amplitude ( Pa ) Time ( s )

Pressure field ( Pa )@ 1 km from the source

Amplitudeis little affected

Effect is mostly native : Local sound velocity variation

on energy deposition areaNot ray structure

Global deflection given by a ray tracing model

Deflection

Directivity

only depends on

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 14

Effective VolumeEffective Volume

Model driven extrapolation

Near field, CC e

Far field, NC L

Sig

nal a

mpl

itud

e (

dB r

ef 1

P

a )

Son

ic V

olum

e (

dB r

ef 1

km

3 )

Range ( dB ref 1 m )

1 km

1 km3

Amplitude ( dB ref 1 Pa )

Signal threshold levels : 1 to 10 mPaEnergies : 1018 to 1020 eV

Model Parameters :Range max, Effective length Leff, effective angular aperture eff

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 15

Boundary effectsBoundary effectsShadowing from the sea bed ( Refraction )

Shadow Zone

Source

Shadow Factor : Efficiency = 1 - F

H = 2500 m depthReceiver zi =448 m

above sea bed

Pure Monte-Carlo

zi = H/2

Mea

n ge

omet

ric

effi

cien

cy (

% )

max/( H/2 )

Water extension is vertically limited

Hypothesis : Direct detectionAt long range

Detection limitedClose to vertical cascades

Analytical & Monte-Carlo

27-30 June 2006 V. Bertin, V. Niess- ARENA 2006 - Newcastle 16

Benchmark Sensitivity EstimatesBenchmark Sensitivity Estimates

Sea Noise 1-10 mPa in B = 100 khz( Ceramic eq. ~ 2-6 mPa )

1018 eV 1020 eV

Mediterranean Sea2500 m depth

(ANTARES like)

1/E2 Flux 1 anE2 ~10-6 GeV·cm-2 · sr-1 · s-1

1 evt/decade/year

Flattening due to boundaries