The Cherenkov Telescope Array Observatory (CTAO) will enable detailed studies of Active Galactic Nuclei (AGN) in the very-high-energy (VHE) regime, as the next-generation ground-based gamma-ray observatory, designed to enhance sensitivity and energy coverage (20 GeV -- 300 TeV) over current Imaging Atmospheric Cherenkov Telescopes (IACTs). In the context of the CTAO Science Collaboration, within the AGN Population working group, we developed a variability-based strategy to improve predictions of AGNs detectable by CTAO, using Fermi-LAT data and normalized excess variance (NXS) as a tracer of flux variability. By extrapolating from 30-day to 3-day timescales, we expanded the sample of sources with short-timescale variability estimates from 87 to 407. This approach allows us to identify flaring and distant AGNs that are promising CTAO targets. The results are being used to support the CTAO extragalactic science program and will be included in an upcoming Consortium publication for the AGN Population collaboration.

DarkSide-20k is a novel liquid argon dark matter detector currently under construction at the Laboratori Nazionali del Gran Sasso (LNGS) of the Istituto Nazionale di Fisica Nucleare (INFN) that will push the sensitivity for Weakly Interacting Massive Particle (WIMP) detection into the neutrino fog. The core of the apparatus is a dual-phase Time Projection Chamber (TPC), filled with 50 tonnes of low radioactivity underground argon (UAr) acting as the WIMP target. NUV-HD-cryo Silicon Photomultipliers (SiPM)s designed by Fondazione Bruno Kessler (FBK) (Trento, Italy) were selected as the photon sensors covering two $$10.5~\text {m}^2$$ 10.5 m 2 Optical Planes, one at each end of the TPC, and a total of $$5~\text {m}^2$$ 5 m 2 photosensitive surface for the liquid argon veto detectors. This paper describes the Quality Assurance and Quality Control (QA/QC) plan and procedures accompanying the production of FBK NUV-HD-cryo SiPM wafers manufactured by LFoundry s.r.l. (Avezzano, AQ, Italy). SiPM characteristics are measured at 77 K at the wafer level with a custom-designed probe station. As of March 2025, 1314 of the 1400 production wafers (94% of the total) for DarkSide-20k were tested. The wafer yield is $$93.2\pm 2.5$$ 93.2 ± 2.5 %, which exceeds the 80% specification defined in the original DarkSide-20k production plan.

The Pierre Auger Observatory is the world’s largest facility dedicated to studying ultra-high-energy cosmic rays (UHECRs). Located in Argentina, it spans 3,000 square kilometers and utilizes a hybrid detection system comprising over 1,600 Water-Cherenkov detectors and fluorescence telescopes. Since its inception in 2004, the Observatory has provided groundbreaking insights into the energy spectrum, mass composition, and arrival direction anisotropies of cosmic rays. Phase-I data analysis, covering the years 2004-2022, has revealed critical features such as large-scale anisotropies and spectral features such as the instep and the suppression of flux at the highest energies, thus advancing our understanding of the origin and propagation of UHECRs. The hybrid detection approach has enabled precise measurements of air showers and muon content, offering constraints on hadronic interaction models. Furthermore, searches for neutral particles have been performed, contributing to multi-messenger astrophysics. The ongoing AugerPrime upgrade aims to refine mass composition studies by integrating scintillator detectors, improved electronics, underground muon detectors, and radio antennas, enhancing sensitivity to primary cosmic-ray properties. We present the key scientific achievements from Phase I and discuss the transformative potential of AugerPrime in addressing fundamental questions about the origin of UHECRs.