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121.
Measuring the muon content of inclined air showers using AERA and the water-Cherenkov detector array of the Pierre Auger Observatory
Marvin Gottowik, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: In this proceeding, we present a proof of principle study for estimating the number of muons of inclined air showers proportional to their energy using hybrid radio and particle detection. We use the radiation energy of an air shower to estimate its electromagnetic energy and measure the muon number independently with the water-Cherenkov detector array (WCD) of the Pierre Auger Observatory. We select 32 high-quality events in almost six years of data with electromagnetic energies above 4 EeV to ensure full efficiency for the WCD reconstruction. The muon content in data is found to be compatible with the one for an iron primary as predicted by current-generation hadronic interaction models. This can be interpreted as a deficit of muons in simulations as a lighter mass composition is expected from �max measurements. Such a muon deficit was already observed in previous analyses of the Auger collaboration and is now confirmed for the first time with radio data. Currently, this analysis is limited by low statistics due to the small area of AERA of 17 km^2 and the high energy threshold. We will outline the advantages of using radio detection instead of the Auger Fluorescence Detector in future analyses allowing for high-statistic measurements of the muon content as a function of energy.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, AERA, water-Cherenkov detector
Objavljeno v RUNG: 23.01.2024; Ogledov: 253; Prenosov: 6
.pdf Celotno besedilo (1,49 MB)
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122.
Status and expected performance of the AugerPrime radio detector
Jannis Pawlowsky, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: 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.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, radio detector, air shower
Objavljeno v RUNG: 23.01.2024; Ogledov: 310; Prenosov: 5
.pdf Celotno besedilo (7,29 MB)
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123.
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: 308; Prenosov: 6
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124.
The number of muons measured in hybrid events detected by the Pierre Auger Observatory
Maximilian Stadelmaier, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The number of muons produced in extensive air showers is a reliable proxy for the amount of hadron production that occurs during the shower development. It is, therefore, an important observable in the context of identifying the mass composition of ultrahigh-energy cosmic rays. Beyond LHC energies, however, hadronic multiparticle production as it occurs in air showers from ultrahigh-energy cosmic rays, is poorly understood, and currently there is little to no way to directly test it experimentally. In simulations, current models of hadronic interactions are unable to produce the average number of muons that is measured by multiple air-shower experiments. In this work, we estimate the number of muons in vertical hybrid events detected by both the fluorescence and surface detectors of the Pierre Auger Observatory above a primary energy of 3 EeV. To reconstruct the signal, we use a model of the water-Cherenkov detector responses that is based on air-shower universality. We take into account the effect of the longitudinal shower development on the lateral distribution of the signal at the ground, as well as the primary energy estimated from the calorimetric energy deposition of the air shower. In this way, we are able to estimate the amount of muons created in vertical showers, relative to expectations from simulated showers using modern hadronic interaction models.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, muons, extensive air showers
Objavljeno v RUNG: 23.01.2024; Ogledov: 289; Prenosov: 5
.pdf Celotno besedilo (2,04 MB)
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125.
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: 281; Prenosov: 7
.pdf Celotno besedilo (1,16 MB)
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126.
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: 288; Prenosov: 5
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127.
A novel tool for the absolute end-to-end calibration of fluorescence telescopes : the XY-scanner
Christoph Schäfer, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The Pierre Auger Observatory uses 27 large-aperture wide-angle Schmidt telescopes to measure the longitudinal profile of air showers using the air-fluorescence technique. Up to the year 2013, the absolute calibration of the telescopes was performed by mounting a uniform large-diameter light source on each of the telescopes and illuminating the entire aperture with a known photon flux. Due to the high amount of work and person-power required, this procedure was only carried out roughly once every three years, and a relative calibration was performed every night to track short-term changes. Since 2013, only the relative calibration has been performed. In this paper, we present a novel tool for the absolute end-to-end calibration of the fluorescence detectors, the XY-Scanner. The XY-Scanner uses a portable integrating sphere as a light source, which has been absolutely calibrated. This light source is installed onto a motorized rail system and moved across the aperture of each telescope. We mimic the illumination of the entire aperture by flashing the light source at ∼1700 positions evenly distributed across the telescope aperture. For the absolute calibration of the light source, we built a dedicated setup that uses a NIST-calibrated photodiode to measure the average photon flux and a PMT to track the pulse-to-pulse stability. We present the laboratory setups used to study the characteristics of the employed light sources and discuss the inter-calibration between selected telescopes.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, fluorescence detectors, longitudinal profile
Objavljeno v RUNG: 23.01.2024; Ogledov: 323; Prenosov: 6
.pdf Celotno besedilo (5,33 MB)
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128.
A new cross-check and review of aerosol attenuation measurements at the Pierre Auger Observatory
Violet M. Harvey, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The distribution of aerosols in the atmosphere above cosmic ray fluorescence detectors must be well characterised in order to precisely recover extensive air shower properties such as the calorimetric energy, �, and depth of shower maximum, �max. The Pierre Auger Observatory uses two centrally located laser facilities to measure the vertical aerosol optical depth profile (VAOD) every hour. It is assumed that the night with the clearest atmosphere each year is effectively aerosol free and that it is an appropriate reference to set the absolute scale of VAOD throughout that year. We review the successes of this method and its associated sources of systematic uncertainty, then present a new cross-check of measured VAOD using air shower events observed in stereo mode. Special attention is paid to quantifying the uncertainties on this result. As the technique is only sensitive to VAOD bias at a fixed altitude, we combine it with a study of aerosol profiles independently measured using a less-sensitive Raman lidar system. This allows us to derive a complete model of the upper limit on the possible bias in the average measured VAOD, which we attribute primarily to an uncertainty on whether the annual reference nights are completely aerosol free. We formulate a correction for this bias and apply it retroactively to all VAOD measurements, then repeat the analysis of the complete air shower dataset and discuss the small but significant effect of this new correction on � and �max. This correction is now fully integrated into the Auger analysis chain.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, fluoresecnce detectors, Xmax
Objavljeno v RUNG: 22.01.2024; Ogledov: 298; Prenosov: 5
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129.
Combined fit to the spectrum and composition data measured by the Pierre Auger Observatory including magnetic horizon effects
Juan Manuel González, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The measurements by the Pierre Auger Observatory of the energy spectrum and mass composition of cosmic rays can be interpreted assuming the presence of two extragalactic source populations, one dominating the flux at energies above a few EeV and the other below. To fit the data ignoring magnetic field effects, the high-energy population needs to accelerate a mixture of nuclei with very hard spectra, at odds with the approximate �−2 shape expected from diffusive shock acceleration. The presence of turbulent extragalactic magnetic fields in the region between the closest sources and the Earth can significantly modify the observed CR spectrum with respect to that emitted by the sources, reducing the flux of low-rigidity particles that reach the Earth. We here take into account this magnetic horizon effect in the combined fit of the spectrum and shower depth distributions, exploring the possibility that a spectrum for the high-energy population sources with a shape closer to �^(−2) be able to explain the observations. We find that a large inter-source separation �s and a large magnetic field RMS amplitude within the Local Supercluster region, such that �rms ≃ 100 nG (40 Mpc/�s) √︁25 kpc/�coh, are needed to interpret the data within this scenario, where �coh is the magnetic field coherence length.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, mass composition, extragalactic magnetic fiels
Objavljeno v RUNG: 22.01.2024; Ogledov: 277; Prenosov: 6
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130.
Long-term calibration and stability of the Auger Engineering Radio Array using the diffuse Galactic radio emission
R. M. de Almeida, Andrej Filipčič, Jonathan Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, objavljeni znanstveni prispevek na konferenci

Opis: The Auger Engineering Radio Array (AERA), part of the Pierre Auger Observatory, is currently the largest facility to measure radio emissions from ultra-high energy extensive air showers. It comprises 153 autonomous radio-detector stations, covering an area of 17 km^2, and measures radio waves in the frequency range from 30 to 80 MHz. An accurate description of the detector response is necessary to interpret the data collected by the stations correctly. Previously, this was achieved by measuring the analog chain in the laboratory and simulating and measuring the directional response of the antenna. In this work, we perform an absolute calibration using the continuously monitored sidereal modulation of the diffuse Galactic radio emission. The calibration is performed by comparing the average spectra recorded by the stations with a model of the full radio sky propagated through the system response, including the antenna, filters, and amplifiers. We describe the method to determine the calibration constants for each antenna and present the corresponding results. Furthermore, the behavior of the calibration constants is studied as a function of time. There is no relevant aging effect over a timescale of a decade, which shows that radio detectors could help monitor possible aging effects of other detector systems during long-term operations, stressing their importance in determining an absolute energy scale.
Ključne besede: pierre auger observatory, auger engineering radio array, ultra-high energy cosmic rays, radio detectors
Objavljeno v RUNG: 22.01.2024; Ogledov: 313; Prenosov: 6
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