The investigation of cosmic rays holds significant importance in the realm of particle physics, enabling us to expand our understanding beyond atomic confines. However, the origin and characteristics ...of ultra-high-energy cosmic rays remain elusive, making them a crucial topic of exploration in the field of astroparticle physics. Currently, our examination of these cosmic rays relies on studying the extensive air showers (EAS) generated as they interact with atmospheric nuclei during their passage through Earth’s atmosphere. Accurate comprehension of cosmic ray composition is vital in determining their source. Notably, the muon content of EAS and the atmospheric depth of the shower maximum serve as the most significant indicators of primary mass composition. In this study, we present two novel methods for reconstructing particle densities based on muon counts obtained from underground muon detectors (UMDs) at varying distances to the shower axis. Our methods were analyzed using Monte Carlo air shower simulations. To demonstrate these techniques, we utilized the muon content measurements from the UMD of the Pierre Auger cosmic ray Observatory, an array of detectors dedicated to measuring extensive air showers. Our newly developed reconstruction methods, employed with two distinct UMD data acquisition modes, showcased minimal bias and standard deviation. Furthermore, we conducted a comparative analysis of our approaches against previously established methodologies documented in existing literature.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•We present an improved method to reconstruct a muon lateral distribution function.•Its performance is assessed from 0.25 to 4EeV and zenith angles up to 45°.•The detector resolution is enhanced in ...most simulated cases.•More events are selected to measure the composition of cosmic rays.•The new reconstruction will allow for a better primary mass classification.
Although the origin of ultra high energy cosmic rays is still unknown, significant progress has been achieved in last decades with the construction of large arrays that are currently taking data. One of the most important pieces of information comes from the chemical composition of primary particles. It is well known that the muon content of air showers generated by the interaction of cosmic rays with the atmosphere is rather sensitive to primary mass. Therefore, the measurement of the number of muons at ground level is an essential ingredient to infer the cosmic ray mass composition. In this work we present a new method for reconstructing the muon lateral distribution function with an array of segmented counters. The energy range from 4×1017eV to 2.5×1018eV is considered. For a triangular array spaced at 750m we found that 450m is the optimal distance to evaluate the number of muons. The corresponding statistical and systematic uncertainties of the new and of a previous reconstruction methods are compared. Since the statistical uncertainty of the new reconstruction is less than in the original one, the power to discriminate between heavy and light cosmic ray primaries is enhanced. The detector dynamic range is also extended in the new reconstruction, so events falling closer to a detector can be included in composition studies.
Despite the significant experimental effort made in the last decades, the origin of the ultra-high energy cosmic rays is still largely unknown. Key astrophysical information to identify where these ...energetic particles come from is provided by their chemical composition. It is well known that a very sensitive tracer of the primary particle type is the muon content of the showers generated by the interaction of the cosmic rays with air molecules. We introduce a likelihood function to reconstruct particle densities using segmented detectors with time resolution. As an example of this general method, we fit the muon distribution at ground level using an array of counters like AMIGA, one of the Pierre Auger Observatory detectors. For this particular case we compare the reconstruction performance against a previous method. With the new technique, more events can be reconstructed than before. In addition the statistical uncertainty of the measured number of muons is reduced, allowing for a better discrimination of the cosmic ray primary mass.
We report a measurement of the energy spectrum of cosmic rays for energies above 2.5 × 1018 eV based on 215,030 events recorded with zenith angles below 60°. A key feature of the work is that the ...estimates of the energies are independent of assumptions about the unknown hadronic physics or of the primary mass composition. The measurement is the most precise made hitherto with the accumulated exposure being so large that the measurements of the flux are dominated by systematic uncertainties except at energies above 5 × 1019 eV. The principal conclusions are (1) The flattening of the spectrum near 5 × 1018 eV, the so-called "ankle," is confirmed. (2) The steepening of the spectrum at around 5 × 1019 eV is confirmed. (3) A new feature has been identified in the spectrum: in the region above the ankle the spectral index γ of the particle flux ( ∝ E−γ ) changes from 2.51 ± 0.03 ( stat ) ± 0.05 ( syst ) to 3.05 ± 0.05 ( stat ) ± 0.10 ( syst ) before changing sharply to 5.1 ± 0.3 ( stat ) ± 0.1 ( syst ) above 5 × 1019 eV. (4) No evidence for any dependence of the spectrum on declination has been found other than a mild excess from the Southern Hemisphere that is consistent with the anisotropy observed above 8 × 1018 eV.
The Pierre Auger Cosmic Ray Observatory Aab, A.; Abreu, P.; Aglietta, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2015, Letnik:
798, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The Pierre Auger Observatory, located on a vast, high plain in western Argentina, is the world׳s largest cosmic ray observatory. The objectives of the Observatory are to probe the origin and ...characteristics of cosmic rays above 1017eV and to study the interactions of these, the most energetic particles observed in nature. The Auger design features an array of 1660 water Cherenkov particle detector stations spread over 3000km2 overlooked by 24 air fluorescence telescopes. In addition, three high elevation fluorescence telescopes overlook a 23.5km2, 61-detector infilled array with 750m spacing. The Observatory has been in successful operation since completion in 2008 and has recorded data from an exposure exceeding 40,000km2sryr. This paper describes the design and performance of the detectors, related subsystems and infrastructure that make up the Observatory.
We report a measurement of the energy spectrum of cosmic rays above 2.5 × 1018 eV based on 215 030 events. New results are presented: at about 1.3 × 1019 eV , the spectral index changes from 2.51 ± ...0.03 (stat) ± 0.05 (syst) to 3.05 ± 0.05 (stat) ± 0.10 (syst), evolving to 5.1 ± 0.3 (stat) ± 0.1 (syst) beyond 5 × 1019 eV, while no significant dependence of spectral features on the declination is seen in the accessible range. These features of the spectrum can be reproduced in models with energy-dependent mass composition. The energy density in cosmic rays above 5 × 1018 eV is 5.66 ± 0.03 (stat) ± 1.40 (syst) × 1053 erg Mpc−3.
The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the ...surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30-80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy-corrected for geometrical effects-is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.
The emission of radio waves from air showers has been attributed to the so-called geomagnetic emission process. At frequencies around 50 MHz this process leads to coherent radiation which can be ...observed with rather simple setups. The direction of the electric field induced by this emission process depends only on the local magnetic field vector and on the incoming direction of the air shower. We report on measurements of the electric field vector where, in addition to this geomagnetic component, another component has been observed that cannot be described by the geomagnetic emission process. The data provide strong evidence that the other electric field component is polarized radially with respect to the shower axis, in agreement with predictions made by Askaryan who described radio emission from particle showers due to a negative charge excess in the front of the shower. Our results are compared to calculations which include the radiation mechanism induced by this charge-excess process.
The fluorescence detector of the Pierre Auger Observatory Abreu, P.; Aguirre, C.; Argirò, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2010, Letnik:
620, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The Pierre Auger Observatory is a hybrid detector for ultra-high energy cosmic rays. It combines a surface array to measure secondary particles at ground level together with a fluorescence detector ...to measure the development of air showers in the atmosphere above the array. The fluorescence detector comprises 24 large telescopes specialized for measuring the nitrogen fluorescence caused by charged particles of cosmic ray air showers. In this paper we describe the components of the fluorescence detector including its optical system, the design of the camera, the electronics, and the systems for relative and absolute calibration. We also discuss the operation and the monitoring of the detector. Finally, we evaluate the detector performance and precision of shower reconstructions.
Dark matter particles could be superheavy, provided their lifetime is much longer than the age of the Universe. Using the sensitivity of the Pierre Auger Observatory to ultrahigh energy neutrinos and ...photons, we constrain a specific extension of the Standard Model of particle physics that meets the lifetime requirement for a superheavy particle by coupling it to a sector of ultralight sterile neutrinos. Our results show that, for a typical dark coupling constant of 0.1, the mixing angle θ m between active and sterile neutrinos must satisfy, roughly, θ m ≲ 1.5 × 10 − 6 ( M X / 10 9 GeV ) − 2 for a mass M X of the dark-matter particle between 10 8 GeV and 10 11 GeV . Published by the American Physical Society 2024
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