The GRAND@Auger Prototype for the Giant Radio Array for Neutrino Detection

Abstract: As of early 2025, the GRAND Collaboration operates three prototype arrays: GRANDProto300 in China, GRAND@Nan\c{c}ay in France, and GRAND@Auger in Argentina. The GRAND@Auger prototype was established through an agreement between the GRAND and Pierre Auger Collaborations, repurposing ten Auger Engineering Radio Array (AERA) stations as GRAND detection units. This setup provides a unique opportunity for coincident air-shower detection, enabling direct event-by-event comparison between GRAND@Auger and the well-established Pierre Auger detectors. Such comparisons allow for a detailed assessment of the detection principle and reconstruction capabilities of GRAND. In this contribution, we present an overview of the commissioning and preliminary results of GRAND@Auger, including the measurement of the Galactic background noise and the detection of the first self-triggered candidate event in coincidence with the Pierre Auger Observatory. Both results underscore the role of GRAND@Auger in advancing the GRAND project and refining the techniques required for large-scale radio detection of ultra-high-energy particles.