Studies on the response of a water-Cherenkov detector of the Pierre Auger Observatory to atmospheric muons using an RPC hodoscope

THE PIERRE AUGER COLLABORATION, INCLUYE S MOLLERACH

JOURNAL OF INSTRUMENTATION

IOP PUBLISHING LTD

Lugar: Londres; Año: 2020

1748-0221

Extensive air showers, originating from ultra-high energy cosmic rays, have been suc-cessfully measured through the use of arrays of water-Cherenkov detectors (WCDs). Sophisticatedanalyses exploiting WCD data have made it possible to demonstrate that shower simulations, basedon different hadronic-interaction models, cannot reproduce the observed number of muons at theground. The accurate knowledge of the WCD response to muons is paramount in establishing theexact level of this discrepancy. In this work, we report on a study of the response of a WCD of thePierre Auger Observatory to atmospheric muons performed with a hodoscope made of resistive platechambers (RPCs), enabling us to select and reconstruct nearly 600 thousand single muon trajectorieswith zenith angles ranging from 0 ◦ to 55 ◦ . Comparison of distributions of key observables betweenthe hodoscope data and the predictions of dedicated simulations allows us to demonstrate the accu-racy of the latter at a level of 2%. As the WCD calibration is based on its response to atmosphericmuons, the hodoscope data are also exploited to show the long-term stability of the procedure.