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Opis: Various hints for anisotropies in the distribution of arrival directions of ultra-high-energy cosmic rays (UHECRs) have been reported. Still, our poor knowledge about extragalactic and Galactic magnetic fields and about the UHECR mass composition makes it non-trivial to interpret such results in terms of possible models of UHECR sources. In this work, we apply the same analyses that have been performed on the Pierre Auger Observatory and the Telescope Array UHECR data to a variety of Monte Carlo simulations generated according to many different combinations of hypotheses about the sources, composition and magnetic deflections of UHECRs. We find that only some of these models can yield results similar to those obtained with the real data.
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, anisotropy, galactic magnetic fields, telescope array, arrival directions
Objavljeno v RUNG: 23.01.2024; Ogledov: 359; Prenosov: 6
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Opis: The measurement of the energy spectrum of ultra-high-energy cosmic rays (UHECRs) is of crucial importance to clarify their origin, acceleration mechanisms, and propagation processes in inter-Galactic and Galactic space. The Pierre Auger Observatory in Argentina and the Telescope Array (TA) in the US have reported their measurements of UHECR energy spectra observed in the southern and northern hemisphere, respectively. The Auger–TA energy spectrum working group was established in 2012 and has been working to understand the uncertainties in energy scale in both experiments, their systematic differences, and differences in the shape of the spectra. In previous works, we reported that there was an overall agreement of the energy spectra measured by the two observatories below 10 EeV while at higher energies, a remaining significant difference was observed in the common declination band. This time we revisit the energy scales of both experiments, including the fluorescence yield and the invisible energy corrections. Another new approach to investigate a possible source of energy systematic difference is to reconstruct simulated showers of common energy and zenith angle using the detector simulation and reconstruction programs of both experiments that are independently tuned and optimized for data from their own detectors. The results will be presented at the conference.
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, Telescope Array, energy spectrum
Objavljeno v RUNG: 23.01.2024; Ogledov: 425; Prenosov: 5
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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: 321; Prenosov: 6
Celotno besedilo (2,50 MB)
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Opis: The Pierre Auger Observatory (Auger) and the Telescope Array (TA), located, respectively, in the Southern and Northern hemispheres, are the largest ultra-high-energy cosmic ray (UHECR) observatories. The Auger and TA Collaborations have collected unprecedented statistics providing us with a unique opportunity to search for the differences between the UHECR energy spectra and mass compositions in the complementary sky regions. To correctly attribute such differences to the properties of the UHECR sources or propagation, the systematic effects in the measurements of each observatory should be considered properly. In this context, the task of the Auger – TA mass composition working group is to identify possible differences of astrophysical origin in the measurements of the depth of the maximum of air-shower profiles, X_max, performed at both observatories using the fluorescence technique. Due to distinct approaches to event selection and analysis atAuger and TA, theworking group uses a specially designed method to transfer the Auger X_max distributions into the TA detector. To this end, dedicated air-shower and detector simulations for the TA Black Rock Mesa and Long Ridge fluorescence detector stations were performed with the Sibyll 2.3d hadronic interaction model. From the comparison of the first two moments and the shapes of X_max distributions for energies above 10^18.2 eV, no significant differences between the Auger and TA measurements were found.
Ključne besede: Pierre Auger Observatory, Telescope Array, ultra-high energy cosmic rays, fluorescence detectors
Objavljeno v RUNG: 22.01.2024; Ogledov: 400; Prenosov: 5
Celotno besedilo (1,19 MB)
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Opis: The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory for gamma-ray astronomy at very-high energies. It will be capable of detecting gamma rays in the energy range from 20 GeV to more than 300 TeV with unprecedented precision in energy and directional reconstruction. With more than 100 telescopes of three different types it will be located in the northern hemisphere at La Palma, Spain, and in the southern at Paranal, Chile. CTA will be one of the largest astronomical infrastructures in the world with open data access and it will address questions in astronomy, astrophysics and fundamental physics in the next decades. In this presentation we will focus on the status of the CTA construction, the status of the telescope prototypes and highlight some of the physics perspectives.
Ključne besede: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array, CTA sensitivity, gamma-ray bursts, POpulation Synthesis Theory Integrated project for very high-energy emission
Objavljeno v RUNG: 04.12.2023; Ogledov: 521; Prenosov: 3
Celotno besedilo (27,92 MB)
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