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1.
Astrophysical interpretation of energy spectrum and mass composition of cosmic rays as measured at the Pierre Auger Observatory
Eleonora Guido, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The combined interpretation of the spectrum and composition measurements plays a key role in the quest for the origin of ultra-high-energy cosmic rays (UHECRs). The Pierre Auger Observatory, thanks to its huge exposure, provides the most precise measurement of the energy spectrum of UHECRs and the most reliable information on their composition, exploiting the distributions of the depth of maximum of the showers in the atmosphere. A combined fit of a simple astrophysical model of UHECR sources to the spectrum and mass composition measurements is used to evaluate the constraining power of the data measured by the Pierre Auger Observatory on the source properties. We find that our data across the “ankle” feature are well reproduced if two extragalactic populations of sources are considered, one emitting a very soft spectrum which dominates the region below the ankle, and the other taking over at energies above the ankle, with an intermediate mixed composition, a hard spectrum and a low rigidity cutoff. Interestingly, similar results can also be obtained if the medium-mass contribution at lower energy is provided by an additional galactic component.
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, UHECR energy spectrum, UHECR mass composition
Objavljeno v RUNG: 24.01.2024; Ogledov: 1053; Prenosov: 7
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2.
Investigation of multi-messenger properties of FR0 radio galaxy emitted ultra-high energy cosmic rays
Jon Paul Lundquist, Lukas Merten, Serguei Vorobiov, Margot Boughelilba, Albert Reimer, Paolo Da Vela, F. Tavecchio, G. Bonnoli, C. Righi, 2023, objavljeni znanstveni prispevek na konferenci

Opis: Low luminosity Fanaroff-Riley type 0 (FR0) radio galaxies are amongst potential contributors to the observed flux of ultra-high energy cosmic rays (UHECRs). Due to FR0s’ much higher abundance in the local universe than more powerful radio galaxies (e.g., about five times more ubiquitous at redshifts z≤0.05 than FR1s), they could provide a substantial fraction of the total UHECR energy density. In the presented work, we determine the mass composition and energy spectrum of UHECRs emitted by FR0 sources by fitting simulation results from the CRPropa3 framework to the recently published Pierre Auger Observatory data. The resulting emission spectral characteristics (spectral indices, rigidity cutoffs) and elemental group fractions are compared to the Auger results. The FR0 simulations include the approximately isotropic distribution of FR0s extrapolated from the measured FR0 galaxy properties and various extragalactic magnetic field configurations, including random and large-scale structured fields. We predict the fluxes of secondary photons and neutrinos produced during UHECR propagation through cosmic photon backgrounds. The presented results allow for probing the properties of the FR0 radio galaxies as cosmic-ray sources using observational high-energy multi-messenger data.
Ključne besede: ultra-high energy cosmic rays, UHECRs, Pierre Auger Observatory, UHECR propagation, UHECR interactions, UHECR energy spectrum, UHECR mass composition, UHECR sources, Fanaroff-Riley (FR) radio galaxies, FR0 galaxies
Objavljeno v RUNG: 24.01.2024; Ogledov: 851; Prenosov: 39
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3.
Measurement of UHECR energy spectrum with the Pierre Auger Observatory and the Telescope Array
Douglas R. Bergman, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, 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, 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: 840; Prenosov: 5
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4.
Measurement of the cosmic ray spectrum with the Pierre Auger Observatory
Daniela Mockler, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci

Opis: The flux of ultra-high energy cosmic rays above 3×10[sup]17 eV has been measured with unprecedented precision at the Pierre Auger Observatory. The flux of the cosmic rays is determined by four different measurements. The surface detector array provides three data sets, two formed by dividing the data into two zenith angle ranges, and one obtained from a nested, denser detector array. The fourth measurement is obtained with the fluorescence detector. By combining all four data sets, the all-sky flux of cosmic rays is determined. The spectral features are discussed in detail and systematic uncertainties are addressed.
Ključne besede: ultra-high-energy cosmic rays (UHECRs), Pierre Auger Observatory, UHECR energy spectrum
Objavljeno v RUNG: 11.10.2023; Ogledov: 1003; Prenosov: 6
.pdf Celotno besedilo (1,66 MB)
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5.
Results from the Pierre Auger Observatory
Esteban Roulet, Andrej Filipčič, Gašper Kukec Mezek, Ahmed Saleh, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, objavljeni znanstveni prispevek na konferenci

Opis: Some of the results on ultrahigh-energy cosmic rays that have been obtained with the Pierre Auger Observatory are presented. These include measurements of the spectrum, composition and anisotropies. Possible astrophysical scenarios that account for these results are discussed.
Ključne besede: ultra-high-energy cosmic rays (UHECRs), Pierre Auger Observatory, UHECR energy spectrum, UHECR anisotropies, UHECR mass composition
Objavljeno v RUNG: 11.10.2023; Ogledov: 1178; Prenosov: 5
.pdf Celotno besedilo (811,90 KB)
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6.
Highlights from the Telescope Array Experiment
J. Kim, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci (vabljeno predavanje)

Opis: The Telescope Array (TA) is the largest ultra-high energy cosmic ray (UHECR) observatory in the Northern Hemisphere. Together with the TA Low Energy Extension (TALE), TA×4, and TALE infill detector, the TA measures the properties of UHECR-induced extensive air showers (EAS) in the energy region from 10^15 eV to over 10^20 eV. Each of these uses a hybrid system with an array of scintillators to sample the footprint of the EAS at the Earth’s surface along with telescopes that measure the fluorescence and Cherenkov light from the EAS. The statistics at the highest energies are being enhanced with the TA×4 detector, half completed but still under construction, which will quadruple the surface detector area with telescopes. The TALE infill surface detectors were recently deployed to further lower the hybrid energy threshold of TALE. We present the status of the experiment and recent results on the energy spectrum, mass composition, and anisotropy, including new features in the energy spectrum at about 10^19.2 eV and in the UHECR arrival direction anisotropy.
Ključne besede: Telescope Array, TALE, low energy extension, TAx4, indirect detection, hybrid detection, ground array, surface detection, fluorescence detection, cerenkov light, ultra-high energy, cosmic rays, energy spectrum, composition, anisotropy
Objavljeno v RUNG: 10.10.2023; Ogledov: 1022; Prenosov: 6
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7.
Measurement of the cosmic ray energy spectrum with the TA×4 SD array
Kozo Fujisue, 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×4 experiment aims to better understand the origin and nature of ultra-high energy cosmic rays (UHECRs) by expanding the observation area of the Telescope Array (TA) experiment by a factor of 4. This expansion will increase the statistics of UHECR events with energies greater than 10^19.5 eV. The SD, which means the additionally deployed surface detectors (SD) for the TA×4 experiment, has been collecting data since 2019, and the analysis of this data is currently underway. In this presentation, we will report comparisons between the Monte Carlo simulation and the data obtained by the TA×4 SD array and highlight the agreement between the two. We will also report on the UHECR energy spectrum observed by the TA×4 SD array from October 2019 to September 2022.
Ključne besede: Telescope Array, TAx4, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, energy spectrum
Objavljeno v RUNG: 09.10.2023; Ogledov: 1026; Prenosov: 7
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8.
Monocular and hybrid analysis for TA×4 fluorescence detectors
Yuki Kusumori, 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×4 project is an extension of the Telescope Array (TA) experiment, aimed at clarifying the origin of the highest energy cosmic rays. It has deployed 4 fluorescence detectors (FDs) and 130 surface detectors (SDs) at the northeast lobe of the original TA array and 8 FDs and 127 SDs at the southeast lobe of the original TA array, expanding the detection area about four times larger than the TA experiment. This expansion enables us to sample larger data. The TA×4 has been collecting data to obtain solid evidence of the excess of events in the arrival direction distribution, known as the TA hotspot, reported in 2014 by the TA experiment. The north and south observations began in 2018 and 2019, respectively, and are ongoing except for a hiatus from February to June 2020 due to the COVID-19 pandemic. In this presentation, we will report the details of TA×4 FD monocular analysis.
Ključne besede: Telescope Array, TAx4, indirect detection, hybrid detection, ground array, fluorescence detection, ultra-high energy, cosmic rays, energy spectrum, composition
Objavljeno v RUNG: 09.10.2023; Ogledov: 1021; Prenosov: 6
.pdf Celotno besedilo (3,20 MB)
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9.
A study of the systematic effects on the energy scale for the measurement of UHECR spectrum by the TA SD array
Keitaro Fujita, R. U. Abbasi, Y. Abe, T. Abu-Zayyad, M. Allen, Yasuhiko Arai, R. Arimura, E. Barcikowski, J. W. Belz, Jon Paul Lundquist, 2023, objavljeni znanstveni prispevek na konferenci

Opis: We evaluated the systematic deviation of energy scales for the energy spectrum of the highest energy cosmic rays observed by the Telescope Array Surface Detector array due to differences in atmospheric fluorescence yield and missing energy estimation. The energy dependence on the energy scales is also investigated and observationally confirmed by the constant intensity cut method analysis. The results of these studies will be presented.
Ključne besede: Telescope Array, indirect detection, surface detection, ground array, fluorescence detection, ultra-high energy, cosmic rays, energy spectrum, fluorescence yield, missing energy, systematics
Objavljeno v RUNG: 09.10.2023; Ogledov: 988; Prenosov: 4
.pdf Celotno besedilo (867,73 KB)
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10.
Performance of the 433 m surface array of the Pierre Auger Observatory
G. Silli, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, objavljeni znanstveni prispevek na konferenci

Opis: The Pierre Auger Observatory, located in western Argentina, is the world's largest cosmic-ray observatory. While it was originally built to study the cosmic-ray flux above 10^18.5 eV, several enhancements have reduced this energy threshold. One such enhancement is a surface array composed of a triangular grid of 19 water-Cherenkov detectors separated by 433 m (SD-433) to explore the energies down to about 10^16 eV. We are developing two research lines employing the SD-433. Firstly, we will measure the energy spectrum in a region where previous experiments have shown evidence of the second knee. Secondly, we will search for ultra-high energy photons to study PeV cosmic-ray sources residing in the Galactic center. In this work, we introduce the SD-433 and we show that it is fully efficient above 5×10^16 eV for hadronic primaries with θ<45∘. Using seven years of data, we present the parametrization of the lateral distribution function of measured signals. Finally, we show that an angular resolution of 1.8∘ (0.5∘) can be attained at the lowest (highest) primary energies. Our study lays the goundmark for measurements in the energy range above 10^16 eV by utilizing the SD-433 and thus expanding the scientific output of the Auger surface detector.
Ključne besede: Pierre Auger Observatory, SD-433, indirect detection, surface detection, low energy extension, ultra-high energy, cosmic rays, energy spectrum, photons, multimessenger
Objavljeno v RUNG: 04.10.2023; Ogledov: 1068; Prenosov: 5
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