acoustic signal computations in the mediterranean sea
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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