BEXCO - Room F(201/202/203/204)
[CRI237] SD rings: peculiar events observed by the surface detector of the Pierre Auger Observatory
The surface detector (SD) of the Pierre Auger Observatory has collected some very peculiar events. The signals produced by these events in the SD stations are very long-lasting compared to those produced by cosmic rays, but the most peculiar characteristic is the footprint of these events on the SD: the stations with a long signal are arranged in a ring with a radius of about 6 km. For some of these events a correlation with lightning strikes was observed. Many checks were performed to exclude the possibility that electronics problems could simulate the observed signals, but these revealed that the peculiar events are indeed produced by particles that cross the Auger water-Cherenkov detectors. A search algorithm was implemented based on the duration of the signal. These events are very sporadic. On a small sample of "golden" events, studies are currently under way to characterize these events, and to understand their origin. The main features of these events will be described and a preliminary reconstruction will be shown.