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Opis: The Pierre Auger Observatory (Auger) and the Telescope Array Project (TA) are the two largest ultra-highenergy cosmic ray (UHECR) observatories in the world. One obstacle in pursuing full-sky UHECR physics is the apparent discrepancy in flux measured by the two experiments. This could be due to astrophysical differences as Auger and TA observe the Southern and Northern skies, respectively. However, the scintillation detectors used by TA have very different sensitivity to the various components of extensive air showers than the water-Cherenkov detectors (WCD) used by Auger. The discrepancy could also be due to systematic effects arising from the differing detector designs and reconstruction methods. The primary goal of the Auger@TA working group is to cross-calibrate the approaches of the two observatories using in-situ methods. This is achieved by placing a self-triggering micro-array, which consists of eight Auger surface detector stations, with both WCDs and AugerPrime scintillators, within the TA array. Seven of the WCDs use a 1-PMT prototype configuration and form a hexagon with the Auger spacing of 1.5 km. The eighth station uses a standard 3-PMT Auger WCD, placed with a TA station at the center of the hexagon to form a triplet for high-statistics, low-uncertainty, cross-calibration of instrumentation. Deployment of the micro-array took place between September 2022 and August 2023, with data-taking foreseen by the Fall of 2023. Details on the instrumentation and deployment of the micro-array, as well as its expected performance, trigger efficiencies, and event rate will be presented. First data from individual stations will also be shown.
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, Telescope Array, AugerPrime, scintillators, water-Cherenkov detectors
Objavljeno v RUNG: 23.01.2024; Ogledov: 345; Prenosov: 6
Celotno besedilo (2,50 MB)
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Opis: We test the hypothesis of an anisotropy laying along the galactic plane which depends on the mass of primary cosmic-rays. The sensitivity to primary mass is provided by the depth of shower maximum, Xmax, from hybrid events measured at the Pierre Auger Observatory. The 14 years of available data are split into on- and off-plane regions using the galactic latitude of each event to form two distributions in Xmax, which are compared using the Anderson-Darling 2-samples test. A scan over a subset of the data is used to select an optimal threshold energy of 10^18.7 eV and a galactic latitude splitting at |b|=30∘, which are then set as a prescription for the remaining data. With these thresholds, the distribution of Xmax from the on-plane region is found to have a 9.1±1.6+2.1−2.2 g/cm2 shallower mean and a 5.9±2.1+3.5−2.5 g/cm2 narrower width than that of the off-plane region. These differences are as such to indicate that the mean mass of primary particles arriving from the on-plane region is greater than that of those coming from the off-plane region. Monte-Carlo studies yield a 4.4σ post-penalization statistical significance for the independent data. Including the scanned data results in a 4.9+1.4−1.5σ post-penalization statistical significance, where the uncertainties are of systematic origin. Accounting for systematic uncertainties leads to an indication for anisotropy in mass composition above 10^18.7 eV at a confidence level of 3.3σ. The anisotropy is observed independently at each of the four fluorescence telescope sites. Interpretations of possible causes of the observed effect are discussed.
Ključne besede: Pierre Auger Observatory, indirect detection, fluorescence detection, ultra-high energy, cosmic rays, composition, anisotropy, Xmax, galactic plane
Objavljeno v RUNG: 03.10.2023; Ogledov: 645; Prenosov: 6
Celotno besedilo (1,33 MB)
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