Radio- -detection of UHECR by detection of UHECR by Radio the - PowerPoint PPT Presentation

CODALEMA CODAL EMA CODAL CODALEMA EMA Collaboration Collaboration Radio- -detection of UHECR by detection of UHECR by Radio the CODALEMA experiment the CODALEMA experiment Olivier RAVEL Olivier RAVEL SUBATECH, Nantes, France and the CODALEMA collaboration Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA CODALEMA CODALEMA setup setup Collaboration Collaboration Scintillator Trigger : 5 central scintillators in coincidence array (trigger) Internal air showers : Energy Known 30 % of uncertainty Dipole array EW polarization of the Electric field Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Collaboration Collaboration Statistics Statistics since December 2006, new setup Effective time : 170 days 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) Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Collaboration Collaboration Energy distribution Energy distribution Number of events, dN/dE Scintillator d i o r a Log E (eV) Histogram not corrected for the acceptance Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Collaboration Collaboration CODALEMA ODALEMA r radio adio- -detection efficiency detection efficiency C (with one Electric field polarization measured) CODALEMA Efficiency Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Collaboration Collaboration Scintillator distributions (internal showers) Shower arrival directions calculated with the scintillator data Azimutal distribution Zenithal distribution Energy threshold for scintillator array ~ 10 15 eV Limited at θ < 50° Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Collaboration Collaboration Shower arrival directions s Shower arrival direction Antenna data 141 radio-detected showers in coincidence with particle detector array Shower deficit in the South direction Small number of events around the Geomagnetic Field Geomagnetic Field Geomagnetic field direction @ Nançay @ Nançay θ = 27 °, = 27 °, φ φ =180° =180° θ Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Collaboration Collaboration Geomagnetic effect Geomagnetic effect Geomagnetic field w e r s h o α North South α : angle between Geomagnetic field and cosmic ray arrival direction Corrected for the triggered events distribution dN/d α Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Collaboration Collaboration Geomagnetic effect / Energy Geomagnetic effect / Energy Energy known only for « internal showers » Log E > 17.5 (CIC method, precision 30 %) 17.3 < Log E < 17.5 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 Geomagnetic Field @ Nançay @ Nançay θ = 27 °, = 27 °, φ φ =180° =180° θ Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Geomagnetic effect / Energy Geomagnetic effect / Energy Collaboration Collaboration Energy known only for « internal showers » (CIC method, precision 30 %) • Low counting rate around the Geomagnetic field • Deficit of low energy events for small α Evidence for a geomagnetic effect Evidence for a geomagnetic effect in the radio emission process in the radio emission process (not only geosynchrotron geosynchrotron) ) (not only Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Electric Field Topology Collaboration Electric Field Topology Collaboration Exponential dependence ε = ε o exp(-d/d o ) E = 2x10 17 eV ε o = 25 µ V/m/MHz ε lectric field ( µ v/m/MHz) Axis distance (meter) Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODAL CODALEMA EMA CODAL CODALEMA EMA Electric Field Topology Electric Field Topology Collaboration Collaboration Exponential dependence ε = ε o exp(-d/d o ) E = 8x10 17 eV ε o = 73 µ V/m/MHz ε lectric field ( µ v/m/MHz) More statistic needed to correlate ε o and Energy Axis distance (meter) Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Electric Field Topology Electric Field Topology Collaboration Collaboration “Giant event” (Energy above 10 18 eV) ε o = 278 µ V/m/MHz Unfortunately ε lectric field ( µ v/m/MHz) not internal HUGE electric field ! Axis distance (meter) Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA CONCLUSION Collaboration Collaboration CODALEMA radio detection efficiency increases with energy Evidence for a Geomagnetic effect Evidence for a Geomagnetic effect radio-detection deficit close to the Geomagnetic field direction effect on the radio-detection efficiency around 10 17 eV constraint on the emission process Detection of all polarization could help At the present time, we do not see clear correlation between the cosmic ray Energy and the measured electric field Larger autonomous antennas array (in 2008 @ Nançay) Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES

CODALEMA CODAL EMA CODAL CODALEMA EMA Collaboration 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 Mérida, 07/07/07 Olivier RAVEL Olivier RAVEL SUBATECH NANTES