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91.
Energy spectrum of cosmic rays measured using the Pierre Auger Observatory
V. Novotný, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, objavljeni znanstveni prispevek na konferenci

Opis: We present the energy spectrum of cosmic rays measured at the Pierre Auger Observatory from 6×10^15 eV up to the most extreme energies where the accumulated exposure reaches about 80 000 km^2sr yr. The wide energy range is covered with five different measurements, namely using the events detected by the surface detector with zenith angles below 60 degrees and applying different reconstruction method also above 60 degrees, those collected by a denser array, the hybrid events simultaneously recorded by the surface and fluorescence detectors, and using those events in which the signal is dominated by Cherenkov light registered by the high-elevation telescopes. In this contribution, we report updates of the analysis techniques and present the spectrum obtained by combining the five different measurements. Spectral features occurring in the wide energy range covered by the Observatory are discussed.
Ključne besede: Pierre Auger Observatory, indirect detection, fluorescence detection, surface detection, hybrid detection, ultra-high energy, cosmic rays, cerenkov light, energy spectrum, inclined showers
Objavljeno v RUNG: 03.10.2023; Ogledov: 484; Prenosov: 5
.pdf Celotno besedilo (1,45 MB)
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92.
Hotspot Update, and a new Excess of Events on the Sky Seen by the Telescope Array Experiment
J. Kim, Jon Paul Lundquist, 2022, objavljeni znanstveni prispevek na konferenci

Opis: The Telescope Array (TA) experiment, the largest observatory studying ultrahigh energy cosmic rays in the northern hemisphere, has reported an excess in the arrival direction distribution for events with energies above 5.7×10^19 eV , called the hotspot. We report here the latest results of the TA hotspot using the most recent data measured by the TA surface detector array, which is more than doubled exposure since the first publication; the hotspot still exists with 3 sigma post-trial significance. By using an oversampling search with a 20∘-circle, similar to the study of the hotspot, we find an additional excess of events at slightly lower energies. The Perseus-Pisces supercluster lies at the location of the new excess. Assuming this structure is responsible for the excess, we conducted a statistical analysis to verify the correlation between observed events and the members of the Perseus-Pisces supercluster.
Ključne besede: Telescope Array, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, anisotropy, hotspot
Objavljeno v RUNG: 03.10.2023; Ogledov: 526; Prenosov: 6
.pdf Celotno besedilo (4,29 MB)
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93.
Reconstruction of air shower events measured by the surface detectors of the TAx4 experiment
H. Jeong, Jon Paul Lundquist, 2022, objavljeni znanstveni prispevek na konferenci

Opis: The source, propagation and acceleration mechanism of ultra-high-energy cosmic rays (UHECR) have been investigated since the first discovery of the UHECRs to solve the mystery of the extremely high-energy universe. The Telescope Array times 4 (TAx4) experiment, which currently consists of 257 Surface Detectors (SDs) and 2 Fluorescence Detector (FD) stations, had been built in Utah, USA in 2019. The TAx4 SDs observe secondary particles in an extensive air shower induced by the UHECR, and we reconstruct arrival direction and energy of the UHECR using the signal intensities and timings measured by the SDs. We present the reconstruction procedure of the UHECR and the preliminary energy spectrum above 10~EeV measured by the TAx4 SDs.
Ključne besede: Telescope Array, TAx4, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, energy spectrum
Objavljeno v RUNG: 03.10.2023; Ogledov: 517; Prenosov: 4
.pdf Celotno besedilo (1,34 MB)
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94.
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: 477; Prenosov: 6
.pdf Celotno besedilo (5,34 MB)
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95.
Large-scale and multipolar anisotropies of cosmic rays detected at the Pierre Auger Observatory with energies above 4 EeV
R. de Almeida, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, objavljeni znanstveni prispevek na konferenci

Opis: More than half a century after the discovery of ultra-high energy cosmic rays (UHECRs), their origin is still an open question. The study of anisotropies in the arrival directions of such particles is an essential ingredient to solve this puzzle. We update our previous analysis of large-scale anisotropies observed by the Pierre Auger Observatory using the latest data collected before the AugerPrime upgrade. We select events with zenith angles up to 80 degrees, implying a sky coverage of 85%, and energies above 4 EeV, for which the surface detector of the Observatory is fully efficient. Dipolar and quadrupolar amplitudes are evaluated through a combined Fourier analysis of the event count rate in right ascension and azimuth. The analysis is performed in three energy bins with boundaries at 4, 8, 16 and 32 EeV and two additional cumulative bins with energies above 8 and 32 EeV. The most significant signal is a dipolar modulation in right ascension for energies above 8 EeV, as previously reported, with statistical significance of 6.6σ. Additionally, we report the measurements of the angular power spectrum for the same energy bins with the same dataset.
Ključne besede: Pierre Auger Observatory, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, anisotropy, dipole, quadropole, angular power spectrum, inclined showers
Objavljeno v RUNG: 03.10.2023; Ogledov: 544; Prenosov: 4
.pdf Celotno besedilo (1,14 MB)
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96.
Joint analysis of the energy spectrum of ultra-high-energy cosmic rays as measured at the Pierre Auger Observatory and the Telescope Array
Y. Tsunesada, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, objavljeni znanstveni prispevek na konferenci

Opis: The measurement of the energy spectrum of ultra-high-energy cosmic rays (UHECRs) is of crucial importance to clarify their origin and acceleration mechanisms. 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 region of the sky accessible to both Observatories ([−15,+24] degrees in declination) can be used to cross-calibrate the two spectra. The Auger-TA energy spectrum working group was organized 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. We revisit this issue to understand its origin by examining the systematic uncertainties, statistical effects, and other possibilities. We will also discuss the differences in the spectra in different declination bands and a new feature in the spectrum recently reported by the Auger Collaboration.
Ključne besede: Telescope Array, Pierre Auger Observatory, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, energy spectrum, anisotropy, declination dependence, fully sky
Objavljeno v RUNG: 02.10.2023; Ogledov: 502; Prenosov: 6
.pdf Celotno besedilo (1,02 MB)
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97.
Telescope Array Combined Fit to Cosmic Ray Spectrum and Composition
D. Bergman, Jon Paul Lundquist, 2022, objavljeni znanstveni prispevek na konferenci

Opis: We present the result of fits of an astrophysical model of UHECR sources to the energy spectrum measured using the Telescope Array (TA) surface detectors and the composition data measured by TA fluorescence detectors in stereo mode. The astrophysical model consists of identical sources, uniformly distributed with a density which evolves with age, where groups of nuclei with varying fractions are accelerated producing a power law source with a rigidity-dependent cutoff. The model includes the propagation effects of photo-pion production, photo-nuclear disintegration and general energy loss from universal expansion. Comparison of model data with detector data in both the energy and the Xmax distributions is done via a forward-folding description of detector effects. A prediction of the cosmogenic neutrino flux at Earth resulting from the cosmic rays produced in the model with these fit values is also presented. The predicted flux is considerably higher than other similar fits to Auger data have previously predicted.
Ključne besede: Telescope Array, indirect detection, stereo detection, fluorescence detection, ultra-high energy, cosmic rays, energy spectrum, composition, combined fit, cosmogenic neutrinos, multimessenger
Objavljeno v RUNG: 02.10.2023; Ogledov: 620; Prenosov: 5
.pdf Celotno besedilo (1,48 MB)
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98.
Telescope Array 10-Year Monocular Spectrum Measurement
D. Bergman, Jon Paul Lundquist, 2022, objavljeni znanstveni prispevek na konferenci

Opis: Telescope Array (TA) is the largest cosmic ray detector in the northern hemisphere. We present a measurement of the cosmic ray energy spectrum for energies above 10^17.5 eV using fluorescence telescopes in monocular mode. A novel weather classification scheme using machine learning was used to select data parts with good weather to ensure the quality of the fluorescence data. The data from the Black Rock Mesa (BR) and Long Ridge (LR) fluorescence telescope stations were analysed separately in monocular mode, with the calculated fluxes combined into a single spectrum. The 10-year monocular combined cosmic ray energy spectrum is in excellent agreement with previous measurements from the northern hemisphere. We present fits of the combined spectrum to a series of broken power law models. A thrice-broken power law is observed to be the best fit considering the Poisson deviance per degrees of freedom. The three breaks suggest an additional feature of the spectrum between the previously observed Ankle at 10^18.7 eV and the GZK suppression at 10^19.8 eV.
Ključne besede: Telescope Array, indirect detection, fluorescence detection, ultra-high energy, cosmic rays, energy spectrum, composition, machine learning, weather classification
Objavljeno v RUNG: 02.10.2023; Ogledov: 560; Prenosov: 5
.pdf Celotno besedilo (1,91 MB)
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99.
Constraining Lorentz Invariance Violation using the muon content of extensive air showers measured at the Pierre Auger Observatory
C. Trimarelli, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, objavljeni znanstveni prispevek na konferenci

Opis: Lorentz symmetry requires the space-time structure to be the same for all observers, but, on the other hand, various quantum gravity theories suggest that it may be violated when approaching the Planck scale. Even a small violation of Lorentz Invariance (LI) could easily affect the Ultra High Energy Cosmic Rays (UHECRs) propagation on a cosmological scale. Moreover, at the extreme energies, like those available in the collision of UHECRs with atmosphere, one should also expect a change in the interactions and, therefore, in the development of extensive air showers. For the first time, this effect has been studied using the muon content of air showers measured at the Pierre Auger Observatory. After having introduced Lorentz Invariance Violation (LIV) as a perturbation term in the single particle dispersion relation, a library of simulated showers with different energies, primary particles and LIV strengths has been produced. Leading to a change in the energy threshold of particle decays, the modification of the energy-momentum relation allows hadronic interactions of neutral pions that contribute to the growth of the hadronic cascade. As a consequence, an increase in the number of muons and a decrease in their intrinsic fluctuations are expected. Comparing the Monte Carlo expectations with the muon fluctuation measurements from the Pierre Auger Observatory, limits on LIV parameters have been derived and presented in this contribution.
Ključne besede: Pierre Auger Observatory, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, muons, air showers, Lorentz violation
Objavljeno v RUNG: 02.10.2023; Ogledov: 582; Prenosov: 6
.pdf Celotno besedilo (1,86 MB)
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100.
Recent measurement of the Telescope Array energy spectrum and observation of the shoulder feature in the Northern Hemisphere
D. Ivanov, Jon Paul Lundquist, 2022, objavljeni znanstveni prispevek na konferenci

Opis: The Telescope Array (TA) is a hybrid cosmic ray detector deployed in 2007 in Millard County, Utah, USA, which consists of a surface detector of 507 plastic scintillation counters spanning a 700 km^2 area on the ground that is overlooked by three fluorescence detector stations. The High Resolution Fly's Eye (HiRes) experiment is a predecessor of TA, which consisted of two fluorescence detector stations operating from 1997 until 2006 from Dugway Proving Ground, Utah, USA, and which was the the first cosmic ray experiment with sufficient resolution and exposure to successfully observe the Greisen–Zatsepin–Kuzmin (GZK) suppression at 10^19.75 eV. In this work, we present an updated TA energy spectrum result and a joint fit of independent spectrum measurements by the TA surface detector, TA fluorescence detector, and HiRes fluorescence detector to a broken power law function, which exhibits the ankle, GZK suppression, and the new shoulder feature initially seen by the Pierre Auger Observatory in the Southern Hemisphere. HiRes and TA observe the shoulder feature in the Northern Hemisphere at 10^19.25 eV, with a statistical significance of 5.3 standard deviations.
Ključne besede: Telescope Array, High Resolution Fly's Eye, HiRes, indirect detection, hybrid detection, ground array, fluorescence detection, ultra-high energy, cosmic rays, energy spectrum, GZK
Objavljeno v RUNG: 02.10.2023; Ogledov: 436; Prenosov: 6
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