Rencontres de Moriond 2009
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Rencontres de Moriond 2009. Very High Energy Phenomena in the Universe. RADIODETECTION AND CHARACTERIZATION OF THE COSMIC RAYS AIR SHOWER RADIO EMISSION FOR ENERGIES HIGHER THAN 10 16 eV WITH THE CODALEMA EXPERIMENT. Thomas SAUGRIN. for the CODALEMA collaboration. WHY RADIODETECTION ?.

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Thomas saugrin

Rencontres de Moriond 2009

Very High Energy Phenomena in the Universe

RADIODETECTION AND CHARACTERIZATION OF THE COSMIC RAYS AIR SHOWER RADIO EMISSION FOR ENERGIES HIGHER THAN 1016 eV WITH THE CODALEMA EXPERIMENT

Thomas SAUGRIN

for the CODALEMA collaboration


Thomas saugrin

WHY RADIODETECTION ?

EAS electric field creation mechanisms:

- negative charge excess (Askar’yan, 1962)

- geomagnetic mechanism (Kahn and Lerche, 1965):

- geosynchrotron model (Huege and Falcke, 2000)

- transversal current model (Lasty, Scholten and Werner, 2005)

Features of « classical » EAS detection methods:

But… first experiments (1963-1980) failed to prove EAS radiodetection efficiency

Present experiments on radiodetection: - the LOPES experiment (Germany)

- the CODALEMA experiment (France)

Thomas SAUGRIN


Thomas saugrin

WHY RADIODETECTION ?

WHY RADIODETECTION ?

EAS electric field creation mechanisms:

- negative charge excess (Askar’yan, 1962)

- geomagnetic mechanism (Kahn and Lerche, 1965):

- geosynchrotron model (Huege and Falcke, 2000)

- transversal current model (Lasty, Scholten and Werner, 2005)

Theorical features of EAS radiodetection:

But… first experiments (1963-1980) failed to prove EAS radiodetection efficiency

Present experiments on radiodetection: - the LOPES experiment (Germany)

- the CODALEMA experiment (France)

04/02/2009

Thomas SAUGRIN

Thomas SAUGRIN

3


Thomas saugrin

EXPERIMENTAL CONFIGURATION (2008)

2 overlapping arrays:

Antenna array:

21 antennas

with EW polarization

3 antennas

with NS polarization

Scintillator array:

17 scintillators

trigger of the antenna array

Thomas SAUGRIN


Thomas saugrin

ACTIVE DIPOLAR ANTENNAS

Sensible to the galactic noise

Antenna lobe obtained by simulation (EZNEC software)

Mean signal (V)

Equivalence voltage – electric field obtained by the simulated antenna response

LST time

Thomas SAUGRIN


Thomas saugrin

SCINTILLATOR ARRAY

Trigger rate: 1 evt/ 7 mins

Energythreshold: 1.1015eV

Zenithalacceptance: 0° <  <60°

Informationson EAS:

- Arrival direction

- Shower core position

- Energy estimate (CIC method)

  • 2 different classes of trigger events (5 central stations in coincidence) :

  • Internal events:Station with the maximum signal is not on the border of the array.

  • Correct estimate of shower energy and core position.

  • - External events: Unreliable estimate of shower energy and core position.

Thomas SAUGRIN


Thomas saugrin

DETECTION EFFICIENCY

scintillators

antennas

Radiodetection threshold (~5.1016 eV) > Trigger threshold (1015 eV)

Only a few events can be detected by CODALEMA

CODALEMA can only access to a restricted energy bandwith

Maximal detection efficiency of 50% for an energy of 7.1017 eV

Source of event deficit ?

Thomas SAUGRIN


Thomas saugrin

ARRIVAL DETECTION

Sky map

Covering map

North

North

West

East

West

East

Geomagnetic

axis

South

South

  • Deficit of events in the geomagnetic axis area

  • Uniform azimutal acceptance for the scintillator array:

Strictly a radio effect

Evidence for a geomagnetic effect in the electric field creation mechanism?

Thomas SAUGRIN


Thomas saugrin

INTERPRETATION

Toy model:

  • Hypothesis:

  • Electric fieldproportional to the Lorentz force

  • Electric fieldpolarization in the direction of the Lorentz force (linearpolarization)

Predictedcoveringmap:

u. a.

North

Total Lorentz force (sin α)

West

East

South

Thomas SAUGRIN


Thomas saugrin

INTERPRETATION

Toy model:

  • Hypothesis:

  • Electric fieldproportional to the Lorentz force

  • Electric fieldpolarization in the direction of the Lorentz force (linearpolarization)

Predictedcoveringmap:

North

Total Lorentz force (sin α)

X

Trigger acceptance

(zenithal angle distribution)

West

East

South

Thomas SAUGRIN


Thomas saugrin

INTERPRETATION

Toy model:

  • Hypothesis:

  • Electric fieldproportional to the Lorentz force

  • Electric fieldpolarization in the direction of the Lorentz force (linearpolarization)

Carte de couverture prédite:

Antenna lobe

North

Force de Lorentz totale (sin α)

West

East

South

Thomas SAUGRIN


Thomas saugrin

INTERPRETATION

Toy model:

  • Hypothesis:

  • Electric fieldproportional to the Lorentz force

  • Electric fieldpolarizationin the direction of the Lorentz force (linearpolarization)

Predictedcoveringmap:

North

Total Lorentz force (sin α)

X

Trigger acceptance

(zenithal angle distribution)

West

East

X

Antenna lobe

(EZNEC simulation)

South

Thomas SAUGRIN


Thomas saugrin

INTERPRETATION

Toy model:

  • Hypothesis:

  • Electric fieldproportional to the Lorentz force

  • Electric fieldpolarization in the direction of the Lorentz force (linearpolarization)

Predictedcoveringmap:

North

Total Lorentz force (sin α)

X

Trigger acceptance

(zenithal angle distribution)

West

East

X

Antenna lobe

(EZNEC simulation)

X

South

Projection on East-West axis

(CODALEMA antenna polarization)

Thomas SAUGRIN


Thomas saugrin

INTERPRETATION

Toy model:

  • Hypothesis:

  • Electric fieldproportional to the Lorentz force

  • Electric fieldpolarization in the direction of the Lorentz force (linearpolarization)

SIMULATION

DATA

North

North

Carte de couverture prédite:

Force de Lorentz totale (sin α)

X

Acceptance du trigger particules

(paramétrisation de la distribution en angle zénithal)

West

East

West

East

X

Lobe de l’antenne dipolaire

(logiciel EZNEC)

South

South

X

Simulated covering map only relevant for radiodetection at energy threshold

Thomas SAUGRIN


Thomas saugrin

MODEL – DATA COMPARISON

data

data

toy model

toy model

  • Geomagnetic toy model fits correctly experimental data:

  • in zenithal angle

  • in azimuthal angle (notably the local maximum in the South direction)

Relevant experimental evidence for a geomagnetic effect in the electric field

creation mechanism

Thomas SAUGRIN


Thomas saugrin

NORTH-SOUTH POLARIZATION

Only 3 antennas with North-South polarization: low statistic (90 events)

North

North

East

West

East

West

South

South

Preliminary results show good agreement with simulation

Thomas SAUGRIN


Thomas saugrin

NORTH-SOUTH POLARIZATION

Only 3 antennas with North-South polarization: low statistic (90 events)

PRELIMINARY

Preliminary results show good agreement with simulation

Thomas SAUGRIN


Thomas saugrin

ELECTRIC FIELD LATERAL DISTRIBUTION

Electric field exponential parameterization (Allan):

E(d) αEP . sin α . cos θ. exp(-d/d0)

E0

E0 radio estimator of shower energy ?

E0

E0

Electric field (µV/m)

Electric field (µV/m)

E0/e

E0/e

d0

d0

Distance to the shower axis (m)

Distance to the shower axis (m)

Thomas SAUGRIN


Thomas saugrin

ELECTRIC FIELD LATERAL DISTRIBUTION

Only 25% of the total events allow a relevant estimate of the E0 parameter

Experimental limitations ?

Near threshold detection, size of the antenna array, one polarization measurement

Physical limitations ?

Incomplete parameterization of the electric field ?

Thomas SAUGRIN


Thomas saugrin

ENERGY CORRELATION

PRELIMINARY

For the 44 internaleventswith a relevant estimate of the E0parameter:

Event by event: E0corr= E0 /(cos θ . )

Log10(E0corr)

E0corr (µV/m) = 95,7. (ECIC /1017eV)1,04

σres = 34%

σminradio~ 16%

Log10(ECIC)

- Linear relation between E0corrandECIC

- Radio detector resolution seems to be better than particle detector resolution

In case of exponential lateral distribution, E0is a relevant estimator of the shower energy

(E-E0)/E0

Thomas SAUGRIN


Thomas saugrin

SUMMARY/OUTLOOK

Experimentalevidence for a geomagneticorigin of the electricfield

Energy calibration promising for the future of the method

Drawback of CODALEMA presentexperimentalset-up:

Worknear the detectionthreshold

Small detection surface

Radiodetection energy

threshold of ~5.1016 eV

Restrictedenergybandwith

May explain difficulties of results interpretation

Creation of a dense array

Extension at largest area and to higher energies

Thomas SAUGRIN


Thomas saugrin

NEXT STEPS

  • Autonomous stations :

  • self-triggered

  • measurement of the E-W and N-S polarizations

In 2009:

- 20 stations at Nançay

dense array of 600m x 600m with 44 antennas

- Available for the [email protected] project

large array with a step of ~300m

In 2010:

Extension of CODALEMA with 100 stations (1 km2)

Thomas SAUGRIN


Thomas saugrin

STATISTICS

Thomas SAUGRIN


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