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1.
Study of downward Terrestrial Gamma-ray Flashes with the surface detector of the Pierre Auger Observatory
Roberta Colalillo, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The surface detector (SD) of the Pierre Auger Observatory, consisting of 1660 water-Cherenkov detectors (WCDs), covers 3000 km2 in the Argentinian pampa. Thanks to the high efficiency of WCDs in detecting gammarays, it represents a unique instrument for studying downward Terrestrial Gamma-ray Flashes (TGFs) over a large area. Peculiar events, likely related to downward TGFs, were detected at the Auger Observatory. Their experimental signature and time evolution are very different from those of a shower produced by an ultrahigh-energy cosmic ray. They happen in coincidence with low thunderclouds and lightning, and their large deposited energy at the ground is compatible with that of a standard downward TGF with the source a few kilometers above the ground. A new trigger algorithm to increase the TGF-like event statistics was installed in the whole array. The study of the performance of the new trigger system during the lightning season is ongoing and will provide a handle to develop improved algorithms to implement in the Auger upgraded electronic boards. The available data sample, even if small, can give important clues about the TGF production models, in particular, the shape of WCD signals. Moreover, the SD allows us to observe more than one point in the TGF beam, providing information on the emission angle.
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, surface detectors, extensive air shower, terrestrial gamma-ray flashes
Objavljeno v RUNG: 23.01.2024; Ogledov: 742; Prenosov: 6
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2.
The performances of the upgraded surface detector stations of AugerPrime
Fabio Convenga, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The surface detector of the Pierre Auger Observatory is an array of 1,600 stations using a water Cherenkov detector (WCD) for particle detection. The array is undergoing a major upgrade known as AugerPrime that involves adding scintillator surface detectors (SSDs) and radio antennas to the existing WCDs. Each WCD is also equipped with a smaller photomultiplier tube added to the original ones. As part of the upgrade, underground muon detectors are being installed in an area with a higher density of surface detector stations. AugerPrime required the development of new electronics to process the signals from all the new detectors and handle a higher sampling rate, a more precise GPS receiver, an extended dynamic range, higher processing capacity, and improved monitoring systems and memory. The deployment of the SSDs on top of each surface detector station is currently completed together with the deployment of the new electronics. This contribution will present the first data from the upgraded stations, emphasizing the performances of the SSDs and the new electronics.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, extensive air showers, scintillation surface detectors
Objavljeno v RUNG: 23.01.2024; Ogledov: 788; Prenosov: 5
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3.
Measurements of cloud base height and coverage using elastic multiangle lidar scans at the Pierre Auger Observatory
Juan Pallotta, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: Cloud features significantly affect the reconstruction of extensive air showers, and their characterization plays an important role in atmospheric monitoring. A multi-directional characterization of the cloud pattern is provided by a combination of several instruments of the atmospheric monitoring network at the Pierre Auger Observatory (Mendoza Province, Argentina). In this work, we present the results of an analysis of the cloud measurements using data taken from 2007 to 2022 by the elastic lidars positioned in the proximity of the fluorescence detector (FD) sites. These systems provide hourly measurements of cloud coverage and base height above FD. The ansatz of horizontal homogeneity of cloud structures is tested by comparing the hourly measurements of cloud base height and coverage done simultaneously at different lidar locations. These results allow a detailed description of cloud patterns observed above the array throughout the whole period. The variation of cloud parameters is shown and quantitative conclusions about cloud homogeneity across the array of the Pierre Auger Observatory are given.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, surface detectors, fluorescence detectors
Objavljeno v RUNG: 23.01.2024; Ogledov: 726; Prenosov: 6
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4.
Deep-learning-based cosmic-ray mass reconstruction using the water-Cherenkov and scintillation detectors of AugerPrime
Niklas Langner, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: At the highest energies, cosmic rays can be detected only indirectly by the extensive air showers they create upon interaction with the Earth’s atmosphere. While high-statistics measurements of the energy and arrival directions of cosmic rays can be performed with large surface detector arrays like the Pierre Auger Observatory, the determination of the cosmic-ray mass on an event-by-event basis is challenging. Meaningful physical observables in this regard include the depth of maximum of air-shower profiles, which is related to the mean free path of the cosmic ray in the atmosphere and the shower development, as well as the number of muons that rises with the number of nucleons in a cosmic-ray particle. In this contribution, we present an approach to determine both of these observables from combined measurements of water-Cherenkov detectors and scintillation detectors, which are part of the AugerPrime upgrade of the Observatory. To characterize the time-dependent signals of the two detectors both separately as well as in correlation to each other, we apply deep learning techniques. Transformer networks employing the attention mechanism are especially well-suited for this task. We present the utilized network concepts and apply them to simulations to determine the precision of the event-by-event mass reconstruction that can be achieved by the combined measurements of the depth of shower maximum and the number of muons.
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, muons, extensive air showers, surface detectors, AugerPrime, deep learning techiniques
Objavljeno v RUNG: 23.01.2024; Ogledov: 635; Prenosov: 7
.pdf Celotno besedilo (2,93 MB)
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5.
Investigating multiple ELVES and halos above strong lightning with the fluorescence detectors of the Pierre Auger Observatory
Roberto Mussa, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: ELVES are being studied since 2013 with the twenty-four FD Telescopes of the Pierre Auger Observatory, in the province of Mendoza (Argentina), the world’s largest facility for the study of ultra-high energy cosmic rays. This study exploits a dedicated trigger and extended readout. Since December 2020, this trigger has been extended to the three High Elevation Auger Telescopes (HEAT), which observe the night sky at elevation angles between 30 and 60 degrees, allowing a study of ELVES from closer lightning. The high time resolution of the Auger telescopes allows us to upgrade reconstruction algorithms and to do detailed studies on multiple ELVES. The origin of multiple elves can be studied by analyzing the time difference and the amplitude ratio between flashes and comparing them with the properties of radio signals detected by the ENTLN lightning network since 2018. A fraction of multi-ELVES can also be interpreted as halos following ELVES. Halos are disc-shaped light transients emitted at 70-80 km altitudes, appearing at the center of the ELVES rings, due to the rearrangement of electric charges at the base of the ionosphere after a strong lightning event.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, surface detectors, fluorescence detectors
Objavljeno v RUNG: 23.01.2024; Ogledov: 671; Prenosov: 5
.pdf Celotno besedilo (9,35 MB)
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6.
The dynamic range of the upgraded surfac-detector stations of AugerPrime
Gioacchino Alex Anastasi, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The detection of ultra-high-energy cosmic rays by means of giant detector arrays is often limited by the saturation of the recorded signals near the impact point of the shower core at the ground, where the particle density dramatically increases. The saturation affects in particular the highest energy events, worsening the systematic uncertainties in the reconstruction of the shower characteristics. The upgrade of the Pierre Auger Observatory, called AugerPrime, includes the installation of an 1-inch Small PhotoMultiplier Tube (SPMT) inside each water-Cherenkov station (WCD) of the surface detector array. The SPMT allows an unambiguous measurement of signals down to about 250m from the shower core, thus reducing the number of events featuring a saturated station to a negligible level. In addition, a 3.8m2 plastic scintillator (Scintillator Surface Detector, SSD) is installed on top of each WCD. The SSD is designed to match the WCD (with SPMT) dynamic range, providing a complementary measurement of the shower components up to the highest energies. In this work, the design and performances of the upgraded AugerPrime surface detector stations in the extended dynamic range are described, highlighting the accuracy of the measurements. A first analysis employing the unsaturated signals in the event reconstruction is also presented.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, fluorescence detectors, scintillator surface detectors
Objavljeno v RUNG: 23.01.2024; Ogledov: 783; Prenosov: 6
.pdf Celotno besedilo (616,96 KB)
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7.
Depth of maximum of air-shower profiles above ▫$10^{17.8}$▫ eV measured with the fluorescence detector of the Pierre Auger Observatory and mass-composition implications
Thomas Fitoussi, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: After seventeen years of operation, the first phase of measurements at the PierreAuger Observatory finished and the process of upgrading it began. In this work, we present distributions of the depth of air-shower maximum, �max, using profiles measured with the fluorescence detector of the Pierre Auger Observatory. The analysis is based on the Phase I data collected from 01 December 2004 to 31 December 2021. The �max measurements take advantage of an improved evaluation of the vertical aerosol optical depth and reconstruction of the shower profiles. We present the energy dependence of the mean and standard deviation of the �max distributions above 10^(17.8) eV. Both �max moments are corrected for detector effects and interpreted in terms of the mean logarithmic mass and variance of the masses by comparing them to the predictions of post-LHC hadronic interaction models. We corroborate our earlier findings regarding the change of the elongation rate of the mean �max at 10^(18.3) eV with higher significance. We also confirm, with four more years of data compared to the last results presented in 2019, that around the ankle in the cosmic rays spectrum, the proton component gradually disappears and that intermediate mass nuclei dominate the composition at ultra-high energies.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, protons, surface detector
Objavljeno v RUNG: 23.01.2024; Ogledov: 656; Prenosov: 7
.pdf Celotno besedilo (1,16 MB)
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8.
Reconstruction of muon number of air showers with the surface detector of the Pierre Auger Observatory using neural networks
Steffen Traugott Hahn, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: To understand the physics of cosmic rays at the highest energies, it is mandatory to have an accurate knowledge of their mass composition. Since the mass of the primary particles cannot be measured directly, we have to rely on the analysis of mass-sensitive observables to gain insights into this composition. A promising observable for this purpose is the number of muons at the ground relative to that of an air shower induced by a proton primary of the same energy and inclination angle, commonly referred to as the relative muon number �μ. Due to the complexity of shower footprints, the extraction of �μ from measurements is a challenging task and intractable to solve using analytic approaches. We, therefore, reconstruct �μ by exploiting the spatial and temporal information of the signals induced by shower particles using neural networks. Using this data-driven approach permits us to tackle this task without the need of modeling the underlying physics and, simultaneously, gives us insights into the feasibility of such an approach. In this contribution, we summarize the progress of the deep-learning-based approach to estimate �μ using simulated surface detector data of the Pierre Auger Observatory. Instead of using single architecture, we present different network designs verifying that they reach similar results. Moreover, we demonstrate the potential for estimating �μ using the scintillator surface detector of the AugerPrime upgrade.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, AugerPrime, surface detector
Objavljeno v RUNG: 23.01.2024; Ogledov: 746; Prenosov: 5
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9.
Mass composition from 3 EeV to 100 EeV using the depth of the maximum of air-shower profiles estimated with deep learning using surface detector data of the Pierre Auger Observatory
Jonas Glombitza, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: We present a new analysis for estimating the depth of the maximum of air-shower profiles, �max, to investigate the evolution of the ultra-high-energy cosmic ray mass composition from 3 to 100 EeV. We use a recently developed deep-learning-based technique for the reconstruction of �max from the data of the surface detector of the Pierre Auger Observatory. To avoid systematic uncertainties arising from hadronic interaction models in the simulation of surface detector data, we calibrate the new reconstruction technique with observations of the fluorescence detector. Using the novel analysis, we have a 10-fold increase of statistics at � > 5 EeV with respect to fluorescence detector data. We are able, for the first time, to study the evolution of the mean and standard deviation of the �max distributions up to 100 EeV. We find an excellent agreement with fluorescence observations and confirm the increase of the mean logarithmic mass ⟨ln(�)⟩ and a decrease of the �max fluctuations with energy. The �max measurement at the highest — so far inaccessible — energies is consistent with a pure mass composition and a mean logarithmic mass of around ∼ 3 (estimated using the Sibyll 2.3d and the EPOS-LHC hadronic interaction models). Furthermore, with the increase in statistics, we find indications for a structure beyond a constant elongation rate in the evolution of �max.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, surface detector, flourescence detector
Objavljeno v RUNG: 22.01.2024; Ogledov: 740; Prenosov: 6
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10.
Investigations of a novel energy estimator using deep learning for the surface detector of the Pierre Auger Observatory
Fiona Ellwanger, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: Exploring physics at energies beyond the reach of human-built accelerators by studying cosmic rays requires an accurate reconstruction of their energy. At the highest energies, cosmic rays are indirectly measured by observing a shower of secondary particles produced by their interaction in the atmosphere. At the Pierre Auger Observatory, the energy of the primary particle is either reconstructed from measurements of the emitted fluorescence light, produced when secondary particles travel through the atmosphere, or shower particles detected with the surface detector at the ground. The surface detector comprises a triangular grid of water-Cherenkov detectors that measure the shower footprint at the ground level. With deep learning, large simulation data sets can be used to train neural networks for reconstruction purposes. In this work, we present an application of a neural network to estimate the energy of the primary particle from the surface detector data by exploiting the time structure of the particle footprint. When evaluating the precision of the method on air shower simulations, we find the potential to significantly reduce the composition bias compared to methods based on fitting the lateral signal distribution. Furthermore, we investigate possible biases arising from systematic differences between simulations and data.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, surface detector, neural network
Objavljeno v RUNG: 22.01.2024; Ogledov: 694; Prenosov: 4
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