Performance and extensions of the central data acquisition system for Phase II of the Pierre Auger Observatory

Abstract: The Pierre Auger Observatory is a hybrid detector designed to observe and study ultra-high-energy particles of extraterrestrial origin. With its 27 fluorescence telescopes and over 1600 autonomously operating water-Cherenkov detectors spread over an area of 3000 km$^2$, it is world-leading in terms of exposure to cosmic rays and offers an unparalleled window into the physical processes that happen at energy scales unattainable by particle accelerators on Earth. Measurement information of candidate air-shower events from all associated detectors and telescopes is collected at a central data-acquisition system located in the nearby town of Malarg\"ue, and processed for higher-level physics analysis. On top of this, data for monitoring the long-term stability and operation of the observatory is forwarded to the central server as well. In this work, we briefly review the central data-acquisition system of the Pierre Auger Observatory. We examine the rates, efficiencies, and purity of detected events for Phase II of the Pierre Auger Observatory and compare them to performance parameters during Phase I. We detail challenges in the event detection up until now and present recent changes in the central data acquisition system and local station software that aim to streamline the data acquisition chain.