41. Monitoring the inter-calibration of the HEAT and Coihueco fluorescence telescopes of the Pierre Auger Observatory with measurements of the brightness of the night skyAlberto Segreto, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The High Elevation Auger Telescopes (HEAT) has increased the Field of View (FoV) of the Fluorescence Detector (FD) at the Coihueco site of the Pierre Auger Observatory and allowed the extension of the energy threshold for the measurements of energies and �max of Extensive Air
Showers (EAS) down to ≈ 1017.2 eV. By temporarily orienting HEAT in the downward position, it acquires data in the same FoV as the other Coihueco telescopes, thus providing the opportunity to intercalibrate the detectors by multiple observations of the same EAS.
To further control systematic uncertainties in �max and energy measurements, in this contribution we present an innovative method that takes advantage of the Night Sky Brightness (NSB) continuously
measured with the FD data acquisition system for monitoring a possible evolution in time of the initial HEAT and Coihueco inter-calibration.
While the brightness of the night sky evolves unpredictably and is highly dependent on local weather conditions, we expect to obtain consistent measurements from telescopes located at the same site and observing the same direction of the sky.
In this work, we describe the method used to compare the NSB measured by the neighboring HEAT and Coihueco telescopes to monitor the stability of their relative calibration over time. This method
allows us to study further the systematics in the inter-calibration of the FD telescopes.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, night sky brightness, high elevation Auger telescopes
Published in RUNG: 22.01.2024; Views: 317; Downloads: 5
 Full text (928,86 KB)
This document has many files! More... |
42. Investigations of a novel energy estimator using deep learning for the surface detector of the Pierre Auger ObservatoryFiona Ellwanger, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: 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.
Keywords: ultra-high energy cosmic rays, Pierre Auger Observatory, surface detector, neural network
Published in RUNG: 22.01.2024; Views: 320; Downloads: 4
Full text (1,78 MB)
This document has many files! More... |
43. Status and performance of the underground muon detector of the Pierre Auger ObservatoryJoaquín De Jesús, 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, located in Malargüe, Argentina, is the largest facility for the detection of ultra-high-energy cosmic rays and has been operating successfully for nearly 20 years. For its second phase of operation, the Observatory is undergoing a major upgrade, called AugerPrime, to increase its sensitivity to the primary mass. As part of the upgrade, the Underground Muon
Detector is being deployed in the low-energy extension of the Surface Detector. It consists of an array of 30 m^2 plastic scintillator muon counters buried 2.3m underground in the vicinity of the water-Cherenkov detectors. This will allow a direct measurement of the muonic component of air showers in the energy range 1016.5 eV to 1019 eV, contributing significantly to the discrimination of the primary mass and to the testing of hadronic interaction models. In this contribution, the deployment status and performance of the Underground Muon Detector are presented.
Keywords: surface detector, Pierre Auger Observatory, AugerPrime, underground muon detector
Published in RUNG: 22.01.2024; Views: 364; Downloads: 5
Full text (15,44 MB)
This document has many files! More... |
44. 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: 360; Downloads: 4
Full text (743,29 KB)
This document has many files! More... |
45. Constraining models for the origin of ultra-high-energy cosmic rays with spectrum, composition, and arrival direction data measured at the Pierre Auger ObservatoryTeresa Bister, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The distribution of cosmic-ray arrival directions shows a better agreement with models in which a fraction of the flux is associated with catalogs of nearby source candidates, such as starburst galaxies, than with isotropy. To investigate this further, we use a novel approach, fitting simultaneously the energy spectrum, distributions of shower maxima, and arrival directions at the highest
energies measured with the Pierre Auger Observatory. The astrophysical model consists of homogeneously distributed background sources as well as an adaptable contribution from nearby source candidates. Propagation effects and a rigidity-dependent magnetic field blurring are taken into account, producing a rising level of anisotropy with the energy. We demonstrate that a model containing a flux fraction of around 20% from the starburst galaxy catalog at 40 EeV, with a hard, nitrogen-dominated injection spectrum, provides a good description of the data. By investigating a scenario with Cen A as a single source in combination with the homogeneous background, we
show that this region of the sky provides the dominant part to the observed anisotropy signal. Models based on jetted active galactic nuclei whose cosmic-ray flux scales with the gamma-ray emission are disfavored. The modeled energy evolution of the arrival directions, the spectra of individual sources, as well as the statistical significance of the results, including the influence of experimental systematic effects, will be discussed in this contribution.
Keywords: anisotropies, Pierre Auger Observatory, ultra-high energy cosmic-rays, arrival directions
Published in RUNG: 22.01.2024; Views: 336; Downloads: 4
Full text (1,47 MB)
This document has many files! More... |
46. An update on the arrival direction studies made with data from the Pierre Auger ObservatoryGeraldina Golup, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution Abstract: The search for anisotropies in the arrival directions of ultra-high-energy cosmic rays plays a key role in the efforts to understand their origin. The observed first-harmonic modulation in right ascension above 8 EeV, detected by the Pierre Auger Observatory with a current significance of 6.9�, suggests an extragalactic origin above this energy. Furthermore, there are indications, at the ∼4� significance level, of anisotropies at intermediate angular scales, which are obtained when comparing the arrival directions against the distribution of potential sources from astrophysical catalogs, in particular that of nearby starburst galaxies, and around the Centaurus region. In this contribution, we present the status of the different searches for anisotropies at small, intermediate
and large angular scales. We use the latest available data set, with 19 years of operation that has yielded 135,000 km^2 yr sr of accumulated exposure, covering the sky at declinations from −90◦ to
45◦. At small and intermediate scales, we report updates of the all-sky blind search for localized excesses, the study around the Centaurus region, and the likelihood analysis with catalogs of
candidate sources. We have also studied the regions of the sky from which the Telescope Array Collaboration has reported hints of excesses in their data and we find no significant effects in
the same directions with a data set of comparable size. At large angular scales, the dipolar and quadrupolar amplitudes in energy bins are updated. We discuss the prospects of these searches,
both in regards to increases in statistics and in relation to the future inclusion of event-by-event mass estimators in these analyses through the upgrade of the Observatory, AugerPrime.
Keywords: anisotropies, Pierre Auger Observatory, ultra-high energy cosmic-rays, arrival directions
Published in RUNG: 22.01.2024; Views: 336; Downloads: 5
Full text (2,45 MB)
This document has many files! More... |
47. Depth of maximum of air-shower profiles : testing the compatibility of the measurements at the Pierre Auger Observatory and the Telescope ArrayA. Abdul Halim, 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 (Auger) and the Telescope Array (TA), located, respectively, in the Southern and Northern hemispheres, are the largest ultra-high-energy cosmic ray (UHECR) observatories. The Auger and TA Collaborations have collected unprecedented statistics providing us with a unique opportunity to search for the differences between the UHECR energy spectra and mass compositions in the complementary sky regions. To correctly attribute such differences to
the properties of the UHECR sources or propagation, the systematic effects in the measurements of each observatory should be considered properly. In this context, the task of the Auger – TA mass composition working group is to identify possible differences of astrophysical origin in the measurements of the depth of the maximum of air-shower profiles, X_max, performed at both observatories using the fluorescence technique. Due to distinct approaches to event selection and analysis atAuger and TA, theworking group uses a specially designed method to transfer the Auger X_max distributions into the TA detector. To this end, dedicated air-shower and detector simulations for the TA Black Rock Mesa and Long Ridge fluorescence detector stations were performed with the Sibyll 2.3d hadronic interaction model. From the comparison of the first two moments and the shapes of X_max distributions for energies above 10^18.2 eV, no significant differences between the Auger and TA measurements were found.
Keywords: Pierre Auger Observatory, Telescope Array, ultra-high energy cosmic rays, fluorescence detectors
Published in RUNG: 22.01.2024; Views: 393; Downloads: 5
Full text (1,19 MB)
This document has many files! More... |
48. Constraining models for the origin of ultra-high-energy cosmic rays with a novel combined analysis of arrival directions, spectrum, and composition data measured at the Pierre Auger ObservatoryA. Abdul Halim, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2024, original scientific article Abstract: The combined fit of the measured energy spectrum and shower maximum depth
distributions of ultra-high-energy cosmic rays is known to constrain the parameters of
astrophysical models with homogeneous source distributions. Studies of the distribution of
the cosmic-ray arrival directions show a better agreement with models in which a fraction of
the flux is non-isotropic and associated with the nearby radio galaxy Centaurus A or with
catalogs such as that of starburst galaxies. Here, we present a novel combination of both
analyses by a simultaneous fit of arrival directions, energy spectrum, and composition data
measured at the Pierre Auger Observatory. The model takes into account a rigidity-dependent magnetic field blurring and an energy-dependent evolution of the catalog contribution shaped by interactions during propagation.
We find that a model containing a flux contribution from the starburst galaxy catalog
of around 20% at 40 EeV with a magnetic field blurring of around 20◦ for a rigidity of
10EV provides a fair simultaneous description of all three observables. The starburst galaxy
model is favored with a significance of 4.5σ (considering experimental systematic effects)
compared to a reference model with only homogeneously distributed background sources.
By investigating a scenario with Centaurus A as a single source in combination with the
homogeneous background, we confirm that this region of the sky provides the dominant
contribution to the observed anisotropy signal. Models containing a catalog of jetted active
galactic nuclei whose flux scales with the γ-ray emission are, however, disfavored as they
cannot adequately describe the measured arrival directions.
Keywords: ultra high energy cosmic rays, cosmic ray experiments, Pierre Auger Observatory, active galactic nuclei
Published in RUNG: 19.01.2024; Views: 392; Downloads: 7
Full text (3,93 MB)
This document has many files! More... |
49. Update on the offline framework for AugerPrime and production of reference simulation libraries using the VO Auger grid resourcesEva 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: 381; Downloads: 7
Full text (1,52 MB)
This document has many files! More... |
50. The Cherenkov Telescope ArrayDaniel Mazin, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, Lukas Zehrer, 2019, published scientific conference contribution Abstract: The Cherenkov Telescope Array (CTA) is the next generation ground-based observatory
for gamma-ray astronomy at very-high energies. It will be capable of detecting gamma rays in the energy range from 20 GeV to more than 300 TeV with unprecedented precision in energy and directional reconstruction. With more than 100 telescopes of three different types it will be located in the northern hemisphere at La Palma, Spain, and in the southern
at Paranal, Chile. CTA will be one of the largest astronomical infrastructures in the world with open data access and it will address questions in astronomy, astrophysics and fundamental physics in the next decades. In this presentation we will focus on the status
of the CTA construction, the status of the telescope prototypes and highlight some of the physics perspectives.
Keywords: very-high-energy gamma-ray astronomy, Cherenkov Telescope Array, CTA sensitivity, gamma-ray bursts, POpulation Synthesis Theory Integrated project for very high-energy emission
Published in RUNG: 04.12.2023; Views: 519; Downloads: 3
Full text (27,92 MB)
This document has many files! More... |
