) Radio Detection of High Energy Showers Sylvie Dagoret-Campagne GDR Neutrinos, IPN, October, 4 2006

GDR Neutrinos, 4-5 october

)Radio Detection of High Energy Showers

● Sylvie Dagoret-CampagneGDR Neutrinos, IPN, October, 4 2006

GDR Neutrinos, 4-5 october 2

History of radio detection of Air Showers

Measure by Vernov at al. (1968)Indicating coherenceWithin a given frequency band

But decoherenceAppears as frequency increasesSpencer (1969) and Allan (1971)

• Started with Jelley in 1964


What can we conclude from a Radio Lateral density Function (RLDF)

• Dependence with– Frequency,– Incident angle,

• Relation to primary energy ?

From Allan (1971)Frequency at 55MHzNormalised pulsesFor 1017eV<E<1019eVθ<30°

Allan,H.R, Havera Park (44 MHz,60MHz) ?


Main questions still open

• Can Radio detection measure the Shower energy ?

• Can Radio detection identify the nature of the Cosmic rays ?

• In the 70’s Radio detection where abandoned in favour of – Particle detection at the ground (scintillators or Cerenkov water

rank),– Then Cerenkov emission was used (pointing on identified

photon sources)– Later in the 90’s the Fluorescence detection was used.


Content

• Usual detection method of Air Showers• Radio emission process

– Cerenkov emission,– Synchrotron emission,– Bremstrahlung emission,– Transition radiation,

• Radar detection• The question of the coherence,• Current experiment in radio detection

– Radio Cerenkov experiments for neutrino detection,– Air Shower Radio detection,

• Test beam experiments that should be done• Radio « detectors»


Usual techniques of

Air Shower detection


Shower developmentShower Scaling parameters:• In Air:

– Rm(asl)=70m

• In Ice:– ρ=0.9g/cm3

– Rm=13cm

– Latt(ν)=100m-1km

– n=1.3 - 1.8• In Rock Salt:

– ρ=2g/cm3

– Rm=

– Latt(ν)~250m-1km

– n=2.45• Lunar regolith (10-20 m depth)

– ρ=1.7g/cm3

– Latt(1GHz)=20m

– n=1.7

Vertical Air Shower(1019eV)

Vertical Air Shower(1019eV)

Nishimura Kamata Greisen

Gaisser Hillas

Rm: Moliere Radius


Radiation of electromagnetic wave by a charged particle

• Generic solution from retarded potentials

• Fourier transform of the radiative part

c

tEntB

ncr

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Radiative part

1019 eVShower inBearth

TF

Loss ofcoherence


Charged Particle Energy loss rate• Ionisation losses of electrons

• Cerenkov energy loss

• Acceleration energy loss

2max

2max

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/234.02

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Fluorescence Yield ~ 4 γ/MeV @ 337nm => energetic Yield ~ 10-5

Cerenkov mayNot be neglectedIn air

(air)


Example of Radio Cerenkov emission in dense media

222

222

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)(

11

)(

ncZ

dX

dNnc

ZddX

dE

•Detected signal in Ice at a given distance (100 m or 500 m)

• Not the same slope vs

Shower energy because coherence appears for radio signal

• Srf ~ Nelec2 (coherence,

for (λ>RM))

• Sopt ~ Nelec (no coherence, for (λ<RM)))


Cerenkov emission in Showers

trc

qixE

nrc

qxE

ee

eee

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crnticrnti

ikr

)/.(

)/.()/.(

11

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In a track step of constant β for a single particle:

The electric field is linearly polarised.

Need charge excess 20 – 30 %:• Compton scattering,•δ rays production,•Positron annihilation,•(Akarian effect)

Contribution inside a Shower :

'

'')).(('3' ),(

),(''

xx

xtJxddt

xE

exxkti

(Zas,Hazen,Stanev parameterisation)


Frequency dependence : coherence- decoherence transition observed for Cerenkov emission in salt

empirical parameterisation:

1

0

0

1

1

1),,(

TeV

E

R

fARE shd

c

A0=2.53x10-7 V/MHzfd=0.52; δ=1.44ν0=1.15 GHzν1=2.86 GHz

hep-ex/0602043 (SLAC testbeam)


Application of Cerenkov emission in dense Media to High Energy Cosmic Neutrinos I


Radio emission detectors (Antenna and Horns) dedicated to neutrino shower detection (US)

FORTE 97-99ν shower detection in Greenland Ice Log periodic antenna,20-300 MHzA=105 km2.sr

GLUE/Goldstone 99:ν shower detectionIn Lunar regolith L andS band (about 2 GHz)A=6.105 km2.sr

ANITA: End 2006ν shower detectionIn Antartica Ice200 MHz - 1.2 GHzA=104 km2.sr


Application of Cerenkov emission of ν induced Showers in Ice or atmopshere:Pioneering radio experiments (FORTE)


Example of Forte neutrino candidate

Frequencychannel

time

Signal : wide band, during few nsBackground: one frequencyLong duration.


Target volume for radio detection: 2 x 105 (km.w.e )3

Application of Cerenkov emission in the Lunar Regolith to detect

High Energy Cosmic Neutrinos



Application of Cerenkov emission of ν induced

Showers in Ice : The anita Concept


SALSA


Existing Neutrino Limits and Potential Future Sensitivity

• RICE limits for 3500 hours livetime

• GLUE limits 123 hours livetime

• ANITA sensitivity, 45 days total:~5 to 30 GZK neutrinos

IceCube: high energy cascades ~1.5-3 GZK events in 3 years

Auger: Tau neutrino decay events ~1 GZK event per year?

SalSA sensitivity, 3 yrs live70-230 GZK neutrino events

Salsita: 4 strings3 events per year

Salsita 3 years


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Geo Synchrotron process in AirShowers

single particle->

Formula usedin particle Shower Monte Carlolike Aires


Radio emission detectors (Antenna and Horns at ground)

Codalema dipole (Nancay)

Codalema log periodic Antenna (Nancay)

Lopes V antenna (KASCADE)

AMBER Horn (Hawai)


Codalema

What is the Radio LDF ?• dependence on incident angles•Frequency dependence•Antenna directivity•Relation to energy (coherence)


Molecular Bremstrahlung

velocityelectronVfrequencycollisionVv

Vv

VvV

c

neV

::)(

)/)((1

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230

3

2

Plasma Emissivity:

•Microwave Molecular Bremsstrahlung Radiation (MBR) in EAS

•Only a small fraction of the available energy budget for secondary isotropic radiation is used up by optical fluorescence.•MBR is simply a subsequent radiative process resulting from the cooling of the EAS plasma.

•The minimum MBR flux can be calculated by considering the emissivity and absorption of a classical bremsstrahlung process.

This process contains a suppression term:


Principe de détection Radar• Illuminer les

gerbes avec un faisceau radar

• Coïncidence détecteur au sol / signal radar

• Gerbes horizontales (standard a haute altitude, neutrinos a basses altitudes)


Radar detection principle


Possibility to measure the longitudinal profile with radar cross section measurement

Ionisation profile density(Aires)

Detection threshold:

The measure of the RCS gives the Fourier transform ofthe ionised electron density

It is proportional to |ne(r)d3r|2

At low frequencyσT=0.665x10-24cm2


Calculs de Section efficaces Radar de gerbes (provenant de la première zone de Fresnel) (P. Gorham,2001)

• La section efficace a un profil approximativement gaussien de FWHW ~ 30°

50 Mhz

30 Mhz

10 Mhz

angle

radar


Ionised electron life time measurement

• The electron lifetime at a few km of altitude constrains the possibility of the radar detection

of vertical showers

• This electron lifetime measurement must be checked/measured in a test beam


Small, overdense meteor, of approximately 0.8s duration.

One long and two small underdense meteors.

Data taken with 67.26 MHz (ch 4) - Pittsburgh Station

(from H. Takai, ANL andBrookhaven)

~ 500 km

Radar routinely used for Meteor detection


Simple Cheap Radar Detection System

Reflected TV signals from meteors, airplanes, … “Homemade” Dipole Antenna (or any TV antenna)

Commercial Radio Receiver

ANL and Brookhaven groups


Frequency Spectrum vs Time in Argonne System: Airplanes and Meteors

Time Frequency

Meteors

Airplanes


• Now proof must establish the connection of Air Shower detection with short time (few ns) Radar echo


Test Beams to validate Radio detection principles, to prove

coherence principe

• Cerenkov Coherence (Askarian principle)– Used for Neutrino Radio detection

• Geo-Synchotron Coherence/incoherence– Used in Air Shower detection

• Molecular Bremstrahlung– Contribution to Air Shower detection

• Transition Radiation– Contribution to Air Shower detection

• Radar detection


Validation of Askarian effect Coherent Radio Cerenkovin sand and salt

NIM A490 (2002) 476astro-ph/0412128

Proof of coherence ? Must show a frequencyCutoff !


MolecularBremstrahlung


Search of Molecular Bremstrahlung at SLAC

Proof of coherence ?Measure of e lifetime ? 60 ns ?


Tests in an electron Beam we would like to do at LAL or IPN to check the Radio emission

• Check of Coherence in Synchrotron emission in a dipole magnetic field,– Coherence never clearly established neither in a circular nor linear

accelerator

– Correction for Transition radiation backscattered at ground ?

• Check the molecular bremstrahlung and measure the electron lifetime in the ionised plasma,– Check results from SLAC test beam results

• Detect the radar echo of the electron beam,– Predicted since a long time, never proved,

• Calibrate our instrumentation using Cerenkov emission in a dense material – (coherence assumed at these frequency)

VHF measure are quite unusual in HEP experiments,Benefit from new technologies (Fast Oscilloscope, FADC above GHZ)


1.Test de l’existence du Bremstrahlung Moleculaire

• Le passage des electrons dans l’air cree un plasma,

• Les electrons ionises du Plasma induisent une emission RF appelee bremstrahlung thermique (en astro) ou moleculaire.

• Le but est de mesurer la duree de vie de colonne d’ionisation, voir de verifier sa densite spectrale

d’emission.

Taille du faisceau variable

1m

0.20m

antenne


2.Test de la diffusion radar

• Le passage des electrons dans l’air cree un plasma

• On essaye de determiner la duree de vie des electrons du plasma en etudiant la forme temporelle de l’echo radar.

• On mesure la section efficace de diffusion Radar

Taille du faisceau variable

Faisceau radar

Antenne réceptric

e

1m

0.20m

Chambre non métallique pour faire varier la

pression

Antenne monitori

ng


3.Test de coherence sur le rayonnement synchrotron

• B=10 G (20 x Bterre)• Ecrit=1.1 10-4 γe

2 B(T) = 4.5.10-5 eV• Rcurv= 3E(GeV)/B(T) =30m• νcrit=67GHz• λcrit=4.5mm

Dipole magnétique (10-100 Gauss)

Electron 10 MeV

Photon synchrotron

détecteur

5m

3m


Coherence never really established

At which frequency this transition occurs ?

Contribution of beam sub-structures ?

Radio Synchrotron spectrum that should be measured with its coherence /decoherence transition

3/44 /5257.0

s

e

incoherent

coherent NPP


Conclusion• There is a wide interest to detect Showers with radio :

– 100 % duty cycle (10 x Fluorescence aperture)– Antenna may be cheaper than Photomultipliers,– Larger acceptance for neutrino detection due to longer

attenuation range,• But one has to prove we can do Air shower measurement with RF

as well as standard techniques:– Energy measurement,– Primary identification,

• Some fundamental questions must be answered like,– Main physical processes involved in radio emission by shower

electrons, Cerenkov radiation, Transition radiation, Synchrotron,– Ionised plasma physics vs altitude and atmospheric composition,

atmospheric condtions (p,T) must be understood, (Bremstrahlung,Radar)

– Coherence effect vs frequency,• Calibration techniques must be found,


backup


Air index

6

2

5

10108.311)(79

1TTT

mbarpn

Documents

) Radio Detection of High Energy Showers Sylvie Dagoret-Campagne GDR Neutrinos, IPN, October, 4 2006