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Radio-detection of UHECR by the CODALEMA experiment

Investigating ultra high energy cosmic rays using radio detection by the CODALEMA experiment in Nantes, France. Analysis of shower arrival directions, geomagnetic effects, and scintillator distributions. Geomagnetic field impact on radio-detection efficiency and electric field topology explored.

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Radio-detection of UHECR by the CODALEMA experiment

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  1. CODALEMA Collaboration Radio-detection of UHECR by the CODALEMA experiment Olivier RAVEL SUBATECH, Nantes, France and the CODALEMA collaboration

  2. CODALEMA Collaboration Trigger: 5 central scintillators in coincidence Internal air showers : Energy Known 30 % of uncertainty CODALEMA setup Scintillator array (trigger) Dipole array EW polarization of the Electric field

  3. CODALEMA Collaboration Statistics Effective time : 170 days (since December 2006, new setup ) Multiplicity >= 3 ( 3 antennas tagged at least) : 613 events Multiplicity >= 3 + time and angular coincidence between both arrays 141 cosmic ray showers radio-detected Counting rate :0.8 events/day 43 showers with energy known (Internal)

  4. CODALEMA Collaboration Energy distribution Scintillator Number of events, dN/dE radio Log E (eV) Histogram notcorrectedfor the acceptance

  5. CODALEMA Collaboration CODALEMAradio-detection efficiency (with one Electric field polarization measured) CODALEMA Efficiency

  6. CODALEMA Collaboration Scintillator distributions (internal showers) Shower arrival directions calculated with the scintillator data Azimutal distribution Zenithal distribution Limited at  < 50° Energy threshold for scintillator array ~ 1015 eV

  7. CODALEMA Collaboration Shower arrival directions Antenna data 141 radio-detected showers in coincidence with particle detector array Shower deficit in the South direction Few events around the Geomagnetic field direction Geomagnetic Field @ Nançay q = 27 °,f =180°

  8. CODALEMA Collaboration Geomagnetic effect Geomagnetic field shower a North South a: angle between Geomagnetic field and cosmic ray arrival direction Corrected for the triggered events distribution dN/da

  9. CODALEMA Collaboration Log E > 17.5 17.3 < Log E < 17.5 Geomagnetic effect / Energy Energy known only for « internal showers » (CIC method, precision 30 %) 17.1 < Log E < 17.3 16.9 < Log E < 17.1 43 internal showers Air showers detected from the South are more energetic Geomagnetic Field @ Nançay q = 27 °,f =180°

  10. CODALEMA Collaboration Evidence for a geomagnetic effect in the radio emission process(not only geosynchrotron) Geomagnetic effect / Energy Energy known only for « internal showers » (CIC method, precision 30 %) • Low counting rate around the Geomagnetic field • Deficit of low energy events for small a

  11. CODALEMA Collaboration electric field (mv/m) Axis distance (meter) Electric Field Topology Exponential dependence e = eo exp(-d/do) E = 2x1017 eV eo= 25 mV/m/MHz

  12. CODALEMA Collaboration Electric Field Topology Exponential dependence e = eo exp(-d/do) E = 8x1017 eV eo= 73 mV/m/MHz electric field (mv/m) More statistic needed to correlate eo and Energy Axis distance (meter)

  13. CODALEMA Collaboration Electric Field Topology “Giant event” (Energy above 1018 eV) Unfortunately not internal eo= 3240 mV/m/MHz HUGE electric field ! electric field (mv/m)

  14. CODALEMA Collaboration constraint on the emission process CONCLUSION CODALEMA radio detection efficiency increases with energy Evidence for a Geomagnetic effect radio-detection deficit close to the Geomagnetic field direction effect on the radio-detection efficiency around 1017eV Detection of all polarization could help At the present time, we do not see clear correlation between the cosmic rayEnergy and the measuredelectric field Larger autonomous antennas array (in 2008 @ Nançay)

  15. CODALEMA Collaboration CODALEMA @ ICRC 2007 see also 3 posters Radiodetection of astronomical phenomena in the cosmic ray dedicated CODALEMA experiment Jacob Lamblin Design and performance of a fully autonomous antenna for radio detection of extensive air showers Benoît Revenu Radio detection of High-Energy cosmic rays at the Pierre Auger Observatory A Van Den Berg

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