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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, published scientific conference contribution

Abstract: 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.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, surface detectors, extensive air shower, terrestrial gamma-ray flashes
Published in RUNG: 23.01.2024; Views: 526; Downloads: 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, published scientific conference contribution

Abstract: 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.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, extensive air showers, scintillation surface detectors
Published in RUNG: 23.01.2024; Views: 477; Downloads: 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, published scientific conference contribution

Abstract: 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.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, surface detectors, fluorescence detectors
Published in RUNG: 23.01.2024; Views: 459; Downloads: 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, published scientific conference contribution

Abstract: 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.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, muons, extensive air showers, surface detectors, AugerPrime, deep learning techiniques
Published in RUNG: 23.01.2024; Views: 439; Downloads: 7
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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, published scientific conference contribution

Abstract: 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.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, surface detectors, fluorescence detectors
Published in RUNG: 23.01.2024; Views: 452; Downloads: 5
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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, published scientific conference contribution

Abstract: 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.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, fluorescence detectors, scintillator surface detectors
Published in RUNG: 23.01.2024; Views: 523; Downloads: 6
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7.
Update on the offline framework for AugerPrime and production of reference simulation libraries using the VO Auger grid resources
Eva Santos, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution

Abstract: Taking data stably since 2004, the Pierre Auger Observatory has published numerous results regarding the properties of ultra-high-energy cosmic rays with unprecedented statistics. However, questions about their origin and mass composition remain unanswered, motivating us to build AugerPrime, a major upgrade of our surface detector array with improved electronics and new detectors. The upgrade is swiftly approaching its completion. Phase II of the Pierre Auger Observatory has begun, which called for an update of the Offline software Framework and modules to handle the additional detectors and the new electronics. Thanks to its modular structure, Offline has proved flexible enough to accommodate all the changes required to handle AugerPrime data reconstruction and event simulation. Additionally, new reference libraries of shower and detector simulations, including dedicated libraries envisaging the searches for neutral particles, such as ultra-high-energy photons and neutrinos, profiting from the new AugerPrime detectors with the upgraded electronics, are in the pipeline. In this contribution, we report on the current status and prospects for the Auger Off line Framework and the production of reference Monte Carlo libraries for AugerPrime.
Keywords: AugerPrime, Pierre Auger Observatory, cosmic rays, surface detectors
Published in RUNG: 16.01.2024; Views: 524; Downloads: 7
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8.
Operations of the Pierre Auger Observatory
R. Caruso, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, published scientific conference contribution

Abstract: The construction of the first stage of the Pierre Auger Observatory, designed for research of ultra-high energy cosmic rays, began in 2001 with a prototype system. The Observatory has been collecting data since early 2004 and was completed in 2008. The Observatory is situated at 1400 m above sea level near Malargüe, (Mendoza province) in western Argentina, covering a vast plain of 3000 squared km, known as the Pampa Amarillo. The Observatory consists of a hybrid detector, in which there are 1660 water-Cherenkov stations, forming the Surface Detector (SD) and 27 peripheral atmospheric fluorescence telescopes, comprising the Fluorescence Detector (FD). Over time, the Auger Observatory has been enhanced with different R&D prototypes and is recently being to an important upgrade called AugerPrime. In the present contribution, the general operations of the SD and FD will be described. In particular the FD shift procedure - executable locally in Malargüe or remotely by teams in control rooms abroad within the Collaboration - and the newly SD shifts (operating since 2019) will be explained. Additionally, the SD and FD maintenance campaigns, as well as the data taking and data handling at a basic level, will be reported
Keywords: Pierre Auger Observatory, AugerPrime, indirect detection, fluorescence detectors, surface detectors, ultra-high energy, cosmic rays, detector operation
Published in RUNG: 04.10.2023; Views: 901; Downloads: 4
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9.
The upgrade of the Pierre Auger Observatory with the Scintillator Surface Detector.
G. Cataldi, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, published scientific conference contribution

Abstract: Since its full commissioning in 2008, the Pierre Auger Observatory has consistently demonstrated its scientific productivity. A major upgrade of the Surface Detector array (SD) improves the capabilities of measuring the different components of extensive air showers. One of the elements of the upgrade consists of new Scintillator Surface Detectors (SSD) placed on top of the Water-Cherenkov stations of the SD. At the Observatory, the integration of the SSD components and their deployment in the array is well advanced. In this paper, the main challenges and characteristics of the construction and installation will be reviewed. Started in 2016, an Engineering Array of twelve upgraded stations has been taking data in the field. In March 2019, a preproduction array of 77 SSDs started data acquisition with an adapted version of non-upgraded electronics. It is collecting events and proving the goodness of SSD design. Since December 2020, the upgraded electronics boards are being deployed in the field together with the photomultiplier tubes, increasing the number of SSD detectors, which are taking data continuosly with good stability. In this paper, the-long term performance of a subset of stations acquiring data for more than two years will be discussed. The data collected so far demonstrate the quality of the new detectors and the physics potential of the upgrade project
Keywords: Pierre Auger Observatory, indirect detection, surface detection, ground array, scintillator surface detectors, ultra-high energy, cosmic rays
Published in RUNG: 04.10.2023; Views: 711; Downloads: 5
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10.
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