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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 10 16 eV WITH THE CODALEMA EXPERIMENT. Thomas SAUGRIN. for the CODALEMA collaboration. WHY RADIODETECTION ?.

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Thomas SAUGRIN

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  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. NORTH-SOUTH POLARIZATION Only 3 antennas with North-South polarization: low statistic (90 events) PRELIMINARY Preliminary results show good agreement with simulation Thomas SAUGRIN

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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 radio@Auger project large array with a step of ~300m In 2010: Extension of CODALEMA with 100 stations (1 km2) Thomas SAUGRIN

  23. STATISTICS Thomas SAUGRIN

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