From the Observation of UHECR Radio Signal in [1-200] MHz to the Composition: CODALEMA and EXTASIS Status Report

Over the years, significant efforts have been devoted to the understanding of the radio emission of extensive air shower (EAS) in the range [20-80] MHz but, despite some studies led until the nineties, the [1-10] MHz band has remained unused for nearly 30 years. The EXTASIS experiment, located within the radio astronomy observatory of Nançay and supported by the CODALEMA instrument, aims to reinvestigate the [1-10] MHz band, and to study the so-called "Sudden Death" contribution, the expected radiation electric field created by the particles that are stopped upon arrival to the ground. We present the instrumental setup and the results obtained with EXTASIS. Moreover, CODALEMA has demonstrated that in [20-80] MHz, the commonly used band, the electric field profile of extensive air showers is well understood, and contains all the information needed for the reconstruction of extensive air showers. An analysis pipeline was developed to set up an online reconstruction of the primary cosmic ray properties. Combining the antenna and acquisition system capabilities, CODALEMA extended the observation window up to 200 MHz, permitting to improve the quality of the reconstruction of the primary cosmic ray properties thanks to a fine calibration procedure. We present the results obtained on a large batch of cosmic ray events, notably a first estimate of their mass dependence with energy.