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1.
Studies of the mass composition of cosmic rays and proton-proton interaction cross-sections at ultra-high energies with the Pierre Auger Observatory
Olena Tkachenko, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: In this work, we present an estimate of the cosmic-ray mass composition from the distributions of the depth of the shower maximum (�max) measured by the fluorescence detector of the Pierre Auger Observatory. We discuss the sensitivity of the mass composition measurements to the uncertainties in the properties of the hadronic interactions, particularly in the predictions of the particle interaction cross-sections. For this purpose, we adjust the fractions of cosmic-ray mass groups to fit the data with �max distributions from air shower simulations. We modify the proton-proton cross-sections at ultra-high energies, and the corresponding air shower simulations with rescaled nucleus-air cross-sections are obtained via Glauber theory. We compare the energydependent composition of ultra-high-energy cosmic rays obtained for the different extrapolations of the proton-proton cross-sections from low-energy accelerator data.
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, extensive air shower, hadronic interactions, cross-section, Xmax
Objavljeno v RUNG: 23.01.2024; Ogledov: 701; Prenosov: 5
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2.
A new cross-check and review of aerosol attenuation measurements at the Pierre Auger Observatory
Violet M. Harvey, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The distribution of aerosols in the atmosphere above cosmic ray fluorescence detectors must be well characterised in order to precisely recover extensive air shower properties such as the calorimetric energy, �, and depth of shower maximum, �max. The Pierre Auger Observatory uses two centrally located laser facilities to measure the vertical aerosol optical depth profile (VAOD) every hour. It is assumed that the night with the clearest atmosphere each year is effectively aerosol free and that it is an appropriate reference to set the absolute scale of VAOD throughout that year. We review the successes of this method and its associated sources of systematic uncertainty, then present a new cross-check of measured VAOD using air shower events observed in stereo mode. Special attention is paid to quantifying the uncertainties on this result. As the technique is only sensitive to VAOD bias at a fixed altitude, we combine it with a study of aerosol profiles independently measured using a less-sensitive Raman lidar system. This allows us to derive a complete model of the upper limit on the possible bias in the average measured VAOD, which we attribute primarily to an uncertainty on whether the annual reference nights are completely aerosol free. We formulate a correction for this bias and apply it retroactively to all VAOD measurements, then repeat the analysis of the complete air shower dataset and discuss the small but significant effect of this new correction on � and �max. This correction is now fully integrated into the Auger analysis chain.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, fluoresecnce detectors, Xmax
Objavljeno v RUNG: 22.01.2024; Ogledov: 675; Prenosov: 5
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3.
Effect of optical properties of FDs on reconstruction analysis
Daiki Sato, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Douglas R. Bergman, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The TA experiment uses fluorescence telescopes to observe cosmic ray air showers. The telescope camera uses PMTs as Pixels. The telescope’s PMT pointing direction has an uncertainty of 0.1°, and more precise measurements of the telescope's optical properties are needed to more accurately reconstruct the cosmic ray air showers. We have developed the Opt-copter which is a light source mounted on a drone that can be flown within the telescope's field of view. Observational experiments with the Opt-copter have provided a more accurate analysis of the telescope viewing direction. In this study, we estimate the effect of this measurement of accurate telescope viewing direction on the reconstruction of cosmic ray air showers.
Ključne besede: Telescope Array, indirect detection, fluorescence detection, ultra-high energy, cosmic rays, composition, calibration, Xmax
Objavljeno v RUNG: 10.10.2023; Ogledov: 972; Prenosov: 6
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4.
Measurement of the Proton-Air Cross Section with Telescope Arrays Black Rock, Long Ridge, and Surface Array in Hybrid Mode.
R. Abbasi, Jon Paul Lundquist, 2022, objavljeni znanstveni prispevek na konferenci

Opis: Ultra High Energy Cosmic Ray (UHECR) detectors have been reporting on the proton-air cross section measurement beyond the capability of particle accelerators since 1984. The knowledge of this fundamental particle property is vital for our understanding of high energy particle interactions and could possibly hold the key to new physics. The data used in this work was collected over eight years using the hybrid events of Black Rock (BR) and Long Ridge (LR) fluorescence detectors as well as the Telescope Array Surface Detector (TASD). The proton-air cross section is determined at s√=73~TeV by fitting the exponential tail of the Xmax distribution of these events. The proton-air cross section is then inferred from the exponential tail fit and from the most updated high energy interaction models. σ^inel_p−air is observed to be 520.1±35.8 [Stat.] +25.3−42.9 [Sys.] mb. This is the second proton-air cross section work reported by the Telescope Array collaboration.
Ključne besede: Telescope Array, indirect detection, hybrid detection, ground array, fluorescence detection, ultra-high energy, cosmic rays, Xmax, proton-air cross-section, high energy particle interaction
Objavljeno v RUNG: 04.10.2023; Ogledov: 958; Prenosov: 4
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5.
Adjustments to Model Predictions of Depth of Shower Maximum and Signals at Ground Level using Hybrid Events of the Pierre Auger Observatory
J. Vicha, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, objavljeni znanstveni prispevek na konferenci

Opis: We present a new method to explore simple ad-hoc adjustments to the predictions of hadronic interaction models to improve their consistency with observed two-dimensional distributions of the depth of shower maximum, Xmax, and signal at ground level, as a function of zenith angle. The method relies on the assumption that the mass composition is the same at all zenith angles, while the atmospheric shower development and attenuation depend on composition in a correlated way. In the present work, for each of the three leading LHC-tuned hadronic interaction models, we allow a global shift ΔXmax of the predicted shower maximum, which is the same for every mass and energy, and a rescaling R_Had of the hadronic component at ground level which depends on the zenith angle. We apply the analysis to 2297 events reconstructed by both fluorescence and surface detectors at the Pierre Auger Observatory with energies 10^18.5−10^19.0 eV. Given the modeling assumptions made in this analysis, the best fit reaches its optimum value when shifting the Xmax predictions of hadronic interaction models to deeper values and increasing the hadronic signal at both extreme zenith angles. The resulting change in the composition towards heavier primaries alleviates the previously identified model deficit in the hadronic signal (commonly called the muon deficit), but does not remove it. Because of the size of the required corrections ΔXmax and R_Had and the large number of events in the sample, the statistical significance of the corrections is large, greater than 5σstat even for the combination of experimental systematic shifts within 1σsys that are the most favorable for the models.
Ključne besede: Pierre Auger Observatory, indirect detection, fluorescence detection, ground array, surface detection, ultra-high energy, cosmic rays, composition, Xmax, muon deficit, air-shower models
Objavljeno v RUNG: 04.10.2023; Ogledov: 845; Prenosov: 6
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6.
Indication of a mass-dependent anisotropy above 10^18.7 eV in the hybrid data of the Pierre Auger Observatory
E.W. Mayotte, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, objavljeni znanstveni prispevek na konferenci

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: 870; Prenosov: 6
.pdf Celotno besedilo (1,33 MB)
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7.
Analysis of TAx4 hybrid trigger and events
S. Kim, Jon Paul Lundquist, 2022, objavljeni znanstveni prispevek na konferenci

Opis: The Telescope Array is the largest ultra-high energy cosmic ray hybrid detector in the Northern hemisphere. While the TAx4 Surface Detector (TAx4 SD) has a duty cycle of ~ 100%, it should be noted that the TAx4 Fluorescence Detector (TAx4 FD) observes the full longitudinal profile of the cosmic ray air showers and therefore is able to determine their energies more accurately than TAx4 SD. In addition, observing cosmic rays in hybrid mode (“hybrid events”) has several advantages. Events seen in hybrid mode by the TAx4 FD and SD are used to establish the energy scale of the TAx4 SD. Moreover, the FD longitudinal profile is used to determine the mass composition of the primary comic ray particles, when the event geometries are well constrained by FD and SD measurements simultaneously. Despite large differences in the TAx4 SD/FD stand-alone performances, both detector types complement each other in measuring important physical quantities. Since August 2019, direction, energy, and Xmax can be obtained from reconstructing hybrid events. In this poster, preliminary analysis of TAx4 hybrid trigger and TAx4 hybrid events will be presented with focus on energy and Xmax observations.
Ključne besede: Telescope Array, TAx4, indirect detection, hybrid detection, hybrid trigger, ground array, fluorescence detection, ultra-high energy, cosmic rays, energy, Xmax
Objavljeno v RUNG: 03.10.2023; Ogledov: 890; Prenosov: 6
.pdf Celotno besedilo (5,34 MB)
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