1. Study of downward Terrestrial Gamma-ray Flashes with the surface detector of the Pierre Auger ObservatoryRoberta 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: 404; Downloads: 6
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2. Studies of the mass composition of cosmic rays and proton-proton interaction cross-sections at ultra-high energies with the Pierre Auger ObservatoryOlena Tkachenko, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: 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.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, extensive air shower, hadronic interactions, cross-section, Xmax
Published in RUNG: 23.01.2024; Views: 345; Downloads: 5
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3. Status and expected performance of the AugerPrime radio detectorJannis Pawlowsky, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The ongoing AugerPrime upgrade of the Pierre Auger Observatory will yield sensitivity and precision for measuring ultra-high energy (UHE) cosmic rays that are significantly improved over the baseline design. A key part is the installation of the Radio Detector (RD), consisting
of loop antennas mounted on top of each of the 1660 water-Cherenkov detectors (WCD). These antennas, with polarizations both parallel and perpendicular to Earth’s magnetic field, are sensitive to inclined air showers and will also improve the sky coverage and exposure of the observatory. Of special interest is the great sensitivity to the electromagnetic component of air showers, yielding new information for the reconstruction of the primary mass, energy and arrival direction. Complementing traditional particle detectors like the WCD, the combination of both yields new opportunities to detect rare primary particles, e.g. UHE photons and neutrinos with a large
identification probability.
Here we present the status and future prospects of the RD.With mass production and deployment ongoing, we showair shower statistics and reconstructions of the already installed detector stations.
We detail the layout and integration of the RD, demonstrating the potential of the observatory including radio measurements and RD triggering, especially to detect air showers with weak particle footprints. We show that the new trigger enables the measurement of events for which traditional particle detectors are less sensitive.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, radio detector, air shower
Published in RUNG: 23.01.2024; Views: 385; Downloads: 5
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4. The time evolution of the surface detector of the Pierre Auger ObservatoryOrazio Zapparrata, 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 array of the Pierre Auger Observatory, consisting of 1660 water Cherenkov tanks, has been in operation for nearly 20 years. During this long period of data acquisition, ageing
effects in the detector response have been observed. The temporal evolution of the signals recorded by the surface detector is mostly compensated by continuous calibration with atmospheric muons;
however, effects persist in the signal rise time and in high-level data analysis using neural networks. We have implemented a detailed description of the time evolution of the detector response and of
the uptimes of individual stations in GEANT4-based detector simulations. These new simulations reproduce the observed time dependencies in the data. Using air-shower simulations that take
into account the evolution of individual stations, we show that the reconstructed energy is stable at the sub-percent level, and its resolution is affected by less than 5% in 15 years. For a few
specific stations, the collected light produced by muons has decreased to the point where it is difficult to distinguish it from the electromagnetic background in the calibration histograms. The
upgrade of the Observatory with scintillator detectors mitigates this problem: by requiring a coincidence between the water-Cherenkov and scintillator detectors, we can enhance the muon relative contribution to the calibration histogram. We present the impact and performance of this coincidence calibration method.
Keywords: surface detector, Pierre Auger Observatory, neural networks, air-shower simulations
Published in RUNG: 22.01.2024; Views: 399; Downloads: 4
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5. Telescope Array Cloud Ranging TestT. Okuda, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: The Telescope Array (TA) experiment detects air-showers induced by ultra high energy cosmic rays. The TA atmospheric Fluorescence telescopic Detector(TAFD) observes cosmic ray airshower, which is incident very far from the telescope. The observation does not take place in overcast night. However, the cloud status changes quickly and sometimes there are some isolated clouds. If the cloud is behind the airshower as viewed from the TAFD, the cloud presents no problem for airshower reconstruction. However if the cloud obscures the airshower, it does create a problem for airshower reconstruction. The problematic event can be rejected by airshower profile at reconstruction. However, the estimation of exposure with isolated cloud is difficult. And it should be affected more at higher energy event with relatively further from the telescope, which is lower statistics and more important for the ultra high energy cosmic ray physics. Therefore, to test the method for evaluating the correction of exposure, we installed stereo cloud cameras near one of FD sites. I report the status of the study of the Telescope Array Cloud Ranging Test.
Keywords: Telescope Array, indirect detection, fluorescence detection, cerenkov light, ultra-high energy, cosmic rays, atmosphere, cloud detection, exposure, air shower reconstruction
Published in RUNG: 04.10.2023; Views: 827; Downloads: 7
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6. Expected performance of the AugerPrime Radio DetectorF. Schlüter, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, published scientific conference contribution Abstract: The AugerPrime Radio Detector will significantly increase the sky coverage of mass-sensitive measurements of ultra-high energy cosmic rays with the Pierre Auger Observatory. The detection of highly inclined air showers with the world’s largest 3000km^2 radio-antenna array in coincidence with the Auger water-Cherenkov detector provides a clean separation of the electromagnetic and muonic shower components. The combination of these highly complementary measurements yields a strong sensitivity to the mass composition of cosmic rays.
We will present the first results of an end-to-end simulation study of the performance of the AugerPrime Radio Detector. The study features a complete description of the AugerPrime radio antennas and reconstruction of the properties of inclined air showers, in particular the electromagnetic energy. The performance is evaluated utilizing a comprehensive set of simulated air showers together with recorded background. The estimation of an energy- and direction-dependent aperture yields an estimation of the expected 10-year event statistics. The potential to measure the number of muons in air showers with the achieved statistics is outlined. Based on the achieved energy resolution, the potential to discriminate between different cosmic-ray primaries is presented.
Keywords: Pierre Auger Observatory, AugerPrime, indirect detection, radio detection, radio antenna array, ultra-high energy, cosmic rays, air-shower muons, composition
Published in RUNG: 04.10.2023; Views: 654; Downloads: 6
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7. Observation of Variations in Cosmic Ray Shower Rates During Thunderstorms and Implications for Large-Scale Electric Field ChangesR. Abbasi, Jon Paul Lundquist, 2022, published scientific conference contribution Abstract: This work presents the first observation by the Telescope Array Surface Detector (TASD) of the effect of thunderstorms on the development of the cosmic ray showers. Observations of variations in the cosmic ray showers, using the TASD, allows us to study the electric field inside thunderstorms on a large scale without dealing with all the limitation of narrow exposure in time and space using balloons and aircraft detectors. In this work, observations of variations in the cosmic ray shower intensity (ΔN/N) using the TASD, was studied and found to be on average at the (1−2)% level. These observations where found to be both negative and positive in polarity. They were found to be correlated with lightning but also with thunderstorms. The size of the footprint of these variations on the ground ranged from (4-24) km in diameter and lasted for 10s of minutes. Dependence of (ΔN/N) on the electric field inside thunderstorms, in this work, is derived from CORSIKA simulations.
Keywords: Telescope Array, indirect detection, surface detection, ground array, ultra-high energy, cosmic rays, shower profile, lightning, atmospheric electric fields
Published in RUNG: 04.10.2023; Views: 540; Downloads: 5
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8. Adjustments to Model Predictions of Depth of Shower Maximum and Signals at Ground Level using Hybrid Events of the Pierre Auger ObservatoryJ. Vicha, Andrej Filipčič, Jon Paul Lundquist, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2022, published scientific conference contribution Abstract: 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.
Keywords: Pierre Auger Observatory, indirect detection, fluorescence detection, ground array, surface detection, ultra-high energy, cosmic rays, composition, Xmax, muon deficit, air-shower models
Published in RUNG: 04.10.2023; Views: 607; Downloads: 6
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9. The fitting procedure for longitudinal shower profiles observed with the fluorescence detector of the Pierre Auger ObservatoryJ. A. Bellido, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The Pierre Auger Observatory uses fluorescence telescopes in conjunction with ground level
particle detectors to measure high-energy cosmic rays and reconstruct, with greater precision,
their arrival direction, their energy and the depth of shower maximum. The depth of shower
maximum is important to infer cosmic ray mass composition. The fluorescence detector is
capable of directly measuring the longitudinal shower development, which is used to reconstruct
the cosmic ray energy and the atmospheric depth of shower maximum. However, given the limited
field of view of the fluorescence detector, the shower profile is not always fully contained within
the detector observation volume. Therefore, considerations need to be taken in order to reconstruct
some events. In this contribution we will describe the method that the Pierre Auger Collaboration
uses to reconstruct the longitudinal profiles of showers and present the details of its performance,
namely its resolution and systematic uncertainties.
Keywords: ultra-high-energy cosmic rays, Pierre Auger Observatory, extensive air showers, longitudinal shower profiles
Published in RUNG: 20.09.2023; Views: 721; Downloads: 6
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10. Estimating the Depth of Shower Maximum using the Surface Detectors of the Pierre Auger ObservatoryCarlos José Todero Peixoto, Andrej Filipčič, Gašper Kukec Mezek, Samo Stanič, Marta Trini, Serguei Vorobiov, Lili Yang, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays (UHECR), extensive air showers, Auger Surface Detector (SD) array, depth
of shower maximum
Published in RUNG: 21.12.2020; Views: 2242; Downloads: 66
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