Radio detection of Cosmic Ray Air Showers The

Radio detection of Cosmic Ray Air Showers The CODALEMA experiment A. Bellétoile for CODALEMA collaboration SUBATECH - Université de Nantes - EMN - IN 2 P 3 Observatoire de Paris-Meudon, Station de Nançay - INSU LAL - IN 2 P 3 ESEO LPSC Grenoble - IN 2 P 3 1

Summary Origin & characteristics of the signal Experimental device First results : evidences for a radio signal associated with CR Air Shower March, 12 th-19 th, 2005 XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 2

Origin & characteristics of the radio signal Production mechanisms: Negative charge excess in the shower n ~10% e- / e+ Charge deflection in the Earth ’s magnetic field n Probably the main contribution Shower direction: n Triangulation Primary particle energy: n Amplitude of the electric field Nature: Detection at large distance is possible March, 12 th-19 th, 2005 Radio detection interests: n Longitudinal profile of the shower (Xmax) XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 3

Theoretical signal Vertical shower @ E = 1017 e. V and small impact parameter H. R. Allan (1971) n pk~150 V/m n FWHM duration ~ 8 ns Broad-band antennas needed n March, 12 th-19 th, 2005 1 -100 MHz XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 4

The Codalema Experiment Decametric Array of the radio observatory of Nançay n n n 144 log periodic antennas Bandwidth 1 -100 MHz High sensitivity Well known & quiet RF environment March, 12 th-19 th, 2005 XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 5

First step: transient detection NW N O E NE 87 m DAM E 800 m 83 m antenna S Trigger (SW) Acquisition n SE 40 -70 MHz DISTANT 1 trigger antenna voltage threshold on a devoted filtered antenna (40 -70 MHz) Simulated x 10 n 0. 5 -5 MHz 5 broad band antennas 8 bits - 500 MS/s - 10 s Off line analysis n n n March, 12 th-19 th, 2005 XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, Numerical filtering (40 -70 MHz) Pulse detection Time tagging 6

Test of triangulation Triangulation n t=2 min n Minimum 3 tagged antennas Plane wave front hypothesis Test on the trajectory of a flying object Field sensitivity n March, 12 th-19 th, 2005 Amplitude rises when distance between source and antenna decreases XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 7

Particle detectors as trigger NW N NE scintillator O E SW S L 1 130 m DAM L 0 antenna SE 130 m L 2 4 particle detectors in coincidence n n ð Active area: 7000 m 2 Counting rate: 0. 7 evt/min Energy threshold: 1. 1015 e. V No particle detectors pollution n March, 12 th-19 th, 2005 No correlation between PM and antenna signal amplitudes XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 8

Time correlation 3 antennas flagged Time correlation distribution n Fortuitous events Flat distribution n Candidates Sharp peak (< 100 ns) March, 12 th-19 th, 2005 XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 9

Arrival direction correlation 2 Fortuitous events n n Lower elevation angle Anthropic sources Good events n n Angular difference ~ 2. 5º RMS 0. 3 evt / day Rough estimation of the energy threshold n March, 12 th-19 th, 2005 > 5. 1016 e. V XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 10

Field topologies (in progress) Variable antenna multiplicity Field amplitudes measured n From 250 V/m to 1. 2 m. V/m in 40 - 70 MHz Extension of the field n n March, 12 th-19 th, 2005 > 100 m more antennas needed XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 11

Conclusion Evidence for radio signal associated with CR Air Showers Operating instrument Codalema program n Additionnal antennas and particle detectors long distance radio signal behavior core position shower energy Stand-alone antennas associated with giant detector March, 12 th-19 th, 2005 XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 12

Transient rate with one antenna as trigger (stand-alone mode) Knowledge of the radio background n n n Atmospheric conditions Human activity Solar activity Low rate n <1 Hz ð 100% duty cycle 2 10 (m. V) March, 12 th-19 th, 2005 XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 13

Simulation of the signal @ E=1020 e. V Vertical shower With charge excess only n n b=0. 5 km : Epeak=1500 V/m FWHM duration=100 ns b=1 km : Epeak=200 V/m FWHM duration = 275 ns broad-band antennas needed n 1 -100 MHz plus n n March, 12 th-19 th, 2005 geomagnetic field contribution expected 10 times greater inclined shower configuration more favourable XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 14

Interaction Scintillators/Antennas Correlation Max antenna/ scintillator signal particles-antennas events (Amplitude Max)2 Antenne D 32 (V) energy deposited in stations No signs of pollution March, 12 th-19 th, 2005 XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, Scintillator signal D 32 (V) 15

Résultats préliminaires Direction d’arrivées scintillateurs Taux de trigger (particules): Pour 4 stations: ~ 0. 7 evt/mn => seuil Eincident~ 1015 e. V limite angulaire : 0° < q <60° pas de limite en F March, 12 th-19 th, 2005 XXXXth Rencontres de Moriond La Thuile , Aosta Valley, , Italia La Thuile, 16