Pierre Auger Observatory and Telescope Array : Joint Contributions to the 34 th International Cosmic Ray Conference ( ICRC 2015 ) The Telescope Array Collaboration

The Pierre Auger Observatory (Auger) in Mendoza, Argentina and the Telescope Array (TA) inUtah, USA aim at unraveling the origin and nature of Ultra-High Energy Cosmic Rays (UHECR).At present, there appear to be subtle differences between Auger and TA results and interpretations.Joint working groups have been established and have already reported preliminary findings. Froman experimental standpoint, the Surface Detectors (SD) of both experiments make use of differentdetection processes not equally sensitive to the components of the extensive air showers makingit to the ground. In particular, the muonic component of the shower measured at ground levelcan be traced back to the primary composition, which is critical for understanding the origin ofUHECRs. In order to make direct comparisons between the SD detection techniques used byAuger and TA, a joint SD experimental research program is being developed. In the first phase,two Auger SD stations were deployed at the TA Central Laser Facility to compare station-levelresponses. This paper concentrates on the results obtained with the first Auger SD station (an“Auger North” design), which has been operating since October 2014. The second Auger SDstation, identical to the ones being operated at Auger in Argentina (an “Auger South” design),was just deployed in June 2015. The second phase of this research program will be to co-locatesix Auger North SD stations with TA stations in the field to compare event-level responses. The 34th International Cosmic Ray Conference30 July – 6 August, 2015The Hague, The Netherlands