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Abstract: Air-Shower universality describes the regularity in the longitudinal, lateral, and energy distributions of electromagnetic shower particles, as motivated by solutions of the cascade equations. To reconstruct air-shower observables from ultra-high-energy cosmic rays, we employ a universality-based model of shower development that incorporates hadronic particle components. Depending on the input parameters, the model can be used, for example, to estimate the depth of the shower maximum or the number of muons on event level. In this context, we present the expected performance for the reconstruction using air-shower simulations and data from the Pierre Auger Observatory.
Keywords: ultra-high-energy cosmic rays, extensive air showers, air-shower universality, Pierre Auger Observatory, UHECR event reconstruction, air-shower maximum depth, muonic shower component
Published in RUNG: 09.06.2025; Views: 328; Downloads: 3
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Abstract: The Pierre Auger Observatory, located near the town Malargüe in the province of Mendoza, Argentina, is the largest cosmic-ray detector in existence, covering an area of 3000 sq. km. The upgraded Observatory, in Phase II of operations, consists of a surface array of 1660 stations combining water Cherenkov, scintillator, and radio detectors. A subset of stations also includes underground muon detectors. Additionally, fluorescence detectors located at four sites overlook the array. The science goals for the enhanced Observatory include the measurement of the properties of ultra-high-energy cosmic rays with large statistics and high sensitivity to the primary composition. The Observatory is also sensitive to photons and neutrinos at the highest energies, allowing it to participate in multi-messenger studies. The Auger Offline Framework provides the tools to perform detailed simulations, using the Geant 4 toolkit, of all components of the Observatory and the analysis of both data and simulated events. It proved to have the flexibility needed to evolve during the lifetime of the Observatory, to accommodate new sub-detectors and, recently, changes to the station readout electronics. A new challenge is interfacing the framework with Machine Learning tools for both the development and execution of neural-network-based algorithms. Independent of the framework, CORSIKA 7 is used to simulate particles, fluorescence light, and radio signals produced by air showers. The production of simulations is coordinated centrally to provide standard libraries for analyses and to optimize the use of computing resources. We will describe the evolution and status of the Offline Framework and the tools used to coordinate the simulation efforts. We will also discuss the challenges of the massive simulation efforts and the resources consumed to provide the simulation libraries required by the Collaboration.
Keywords: ultra-high-energy cosmic rays, Pierre Auger Observatory, air-shower simulations, extensive air showers, detector simulations
Published in RUNG: 29.05.2025; Views: 380; Downloads: 6
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Abstract: This work focuses on estimating the muon density at ground level using simulations and investigating its correlation with the muonic signal recorded by the Water Cherenkov Detectors (WCDs) of the Pierre Auger Observatory. The study is motivated by the need to validate the estimation of the muonic signal in the WCDs. The methodology involves the development of a parameterization for the surface muon density based on simulated muon data from the Underground Muon Detector (UMD) of AugerPrime—an upgrade to the Pierre Auger Observatory. Our results indicate a negligible bias and a resolution better than 40 at energies above 10[sup]17.5 eV. Furthermore, we find a strong positive correlation between the estimated muon density and the simulated muonic signals in the WCDs.
Keywords: ultra-high-energy cosmic rays, Pierre Auger Observatory, extensive air showers, AugerPrime upgrade, muonic air-shower component
Published in RUNG: 29.05.2025; Views: 315; Downloads: 7
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Abstract: The Pierre Auger Observatory has been collecting data for over 19 years, reaching more than 135 000 sq. km yr sr of accumulated exposure, with the surface detectors spread over 3000 sq. km. A remarkable discovery is the large-scale dipole structure with a total amplitude of 7.4% for energies above 8 EeV. The observed modulation in right ascension has a statistical significance of 6.8 sigma. The dipolar pattern in the events with energies between 8 and 16 EeV has a statistical significance of over 5 sigma. The Pierre Auger Collaboration has also reported an increase in the dipole amplitude with energy. This anisotropy is understood to be of extragalactic origin, as the maximum of the dipolar component is located ∼ 115◦ away from the Galactic Center. In the same energy range, the observed evolution of the depth of maximum shower development with energy indicates a progression towards heavier composition of cosmic rays with increasing energy. This contribution presents a novel approach to a search for composition-enhanced large-scale anisotropy. On the one hand, lighter events have higher rigidity than their heavier counterparts with similar energy; therefore, their trajectories are less affected by magnetic fields. The expected effect is a higher anisotropy in the arrival direction of a subset of events with smaller mass and charge than the anisotropy in the overall flux of cosmic rays. On the other hand, the attenuation length is distinct for each mass group, leading to different horizon of cosmic ray sources for each of them. Under a source-agnostic model, we investigate the dipole amplitude as a function of rigidity. Using a simulation library, we analyze the possibility of measuring a separation in total dipole amplitude between two sub-populations distinct in mass of the Auger Phase I dataset.
Keywords: ultra-high-energy cosmic rays, Pierre Auger Observatory, UHECR arrival directions, UHECR mass composition, large-scale anisotropy
Published in RUNG: 29.05.2025; Views: 259; Downloads: 2
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Abstract: The Barcelona Raman LIDAR (BRL) will provide continuous monitoring of the aerosol extinction profile along the line of sight of the Cherenkov Telescope Array Observatory (CTAO). It will be located at its Northern site (CTAO-N) on the Observatorio del Roque de Los Muchachos. This article presents the performance of the pathfinder Barcelona Raman LIDAR (pBRL), a prototype instrument for the final BRL. Power budget simulations were carried out for the pBRL operating under various conditions, including clear nights, moon conditions, and dust intrusions. The LIDAR PreProcessing (LPP) software suite is presented, which includes several new statistical methods for background subtraction, signal gluing, ground layer and cloud detection and inversion, based on two elastic and one Raman lines. Preliminary test campaigns were conducted, first close to Barcelona and later at CTAO-N, albeit during moonlit nights only. The pBRL, under these non-optimal conditions, achieves maximum ranges up to about 35 km, range resolution of about 50 m for strongly absorbing dust layers, and 500 m for optically thin clouds with the Raman channel only, leading to similar resolutions for the LIDAR ratios and Ångström exponents. Given the reasonable agreement between the extinction coefficients obtained from the Raman and elastic lines independently, an accuracy of aerosol optical depth retrieval in the order of 0.05 can be assumed with the current setup. The results show that the pBRL can provide valuable scientific results on aerosol characteristics and structure, although not all performance requirements could be validated under the conditions found at the two test sites. Several moderate hardware improvements are planned for its final upgraded version, such as gated PMTs for the elastic channels and a reduced-power laser with a higher repetition rate, to ensure that the data acquisition system is not saturated and therefore not affected by residual ringing.
Keywords: Barcelona Raman LIDAR, BRL, Cherenkov Telescope Array Observatory, CTAO, remote sensing, lidar, Raman lidar
Published in RUNG: 26.05.2025; Views: 329; Downloads: 5
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