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.
Optical crosstalk in SiPMs Hampel, M.R.; Fuster, A.; Varela, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2020, Letnik:
976
Journal Article
Recenzirano
It was observed that the optical crosstalk probability (CT) of the silicon photomultipliers (SiPMs) of the electronics in all the AMIGA muon counter modules installed at the Pierre Auger Observatory ...was reduced by a factor of ∼2.68 after its deployment. This effect motivated the study of the optical crosstalk in SiPMs, in particular, the external interface optical crosstalk (EICT). In this paper, two laboratory measurements were performed to evaluate the CT, and a model to simulate the EICT is proposed. We show that combining CT measurements with simulations, the EICT can be precisely estimated. We also obtained the internal optical crosstalk of the tested SiPM and it was (1.27±0.05)%. This study shows that the thickness of the protective window of the SiPM and the optical system to which the SiPM is coupled affects optical crosstalk. We conclude that the EICT is not negligible and for some cases it is the main contribution to the total optical crosstalk in SiPMs. Taking advantage of the CT variations depending on the optical system to which the SiPM is connected, we propose a method to validate the proper installation of the electronics in the muon counters modules of AMIGA.
Abstract
Ultra-high-energy photons with energies exceeding 10
17
eV offer a wealth of connections to different aspects of cosmic-ray astrophysics as well as to gamma-ray and neutrino astronomy. The ...recent observations of photons with energies in the 10
15
eV range further motivate searches for even higher-energy photons. In this paper, we present a search for photons with energies exceeding 2 × 10
17
eV using about 5.5 yr of hybrid data from the low-energy extensions of the Pierre Auger Observatory. The upper limits on the integral photon flux derived here are the most stringent ones to date in the energy region between 10
17
and 10
18
eV.
Abstract We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the ...spectrum is observed, confirming the presence of the so-called second-knee feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays.
Abstract
We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the ...spectrum is observed, confirming the presence of the so-called
second-knee
feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays.
Abstract The hybrid design of the Pierre Auger Observatory allows for the measurement of the properties of extensive air showers initiated by ultra-high energy cosmic rays with unprecedented ...precision. By using an array of prototype underground muon detectors, we have performed the first direct measurement, by the Auger Collaboration, of the muon content of air showers between $$2\times 10^{17}$$ 2×1017 and $$2\times 10^{18}$$ 2×1018 eV. We have studied the energy evolution of the attenuation-corrected muon density, and compared it to predictions from air shower simulations. The observed densities are found to be larger than those predicted by models. We quantify this discrepancy by combining the measurements from the muon detector with those from the Auger fluorescence detector at $$10^{{17.5}}\, {\mathrm{eV}} $$ 1017.5eV and $$10^{{18}}\, {\mathrm{eV}} $$ 1018eV . We find that, for the models to explain the data, an increase in the muon density of $$38\%$$ 38% $$\pm 4\% (12\%)$$ ±4%(12%) $$\pm {}^{21\%}_{18\%}$$ ±18%21% for EPOS-LHC, and of $$50\% (53\%)$$ 50%(53%) $$\pm 4\% (13\%)$$ ±4%(13%) $$\pm {}^{23\%}_{20\%}$$ ±20%23% for QGSJetII-04, is respectively needed.
The hybrid design of the Pierre Auger Observatory allows for the measurement of the properties of extensive air showers initiated by ultra-high energy cosmic rays with unprecedented precision. By ...using an array of prototype underground muon detectors, we have performed the first direct measurement, by the Auger Collaboration, of the muon content of air showers between 2 $\times$ 1017 and 2 $\times$ 1018 eV. We have studied the energy evolution of the attenuation-corrected muon density, and compared it to predictions from air shower simulations. The observed densities are found to be larger than those predicted by models. We quantify this discrepancy by combining the measurements from the muon detector with those from the Auger fluorescence detector at 1017.5 eV and 1018 eV. We find that, for the models to explain the data, an increase in the muon density of 38% $±$4%(12%) $±^{21\%}_{18\%}$ for EPOS-LHC, and of 50%(53%) $±$4%(13%) $±^{23\%}_{20\%}$ for QGSJETII-04, is respectively needed.
We report an investigation of the mass composition of cosmic rays with
energies from 3 to 100 EeV (1 EeV=$10^{18}$ eV) using the distributions of the
depth of shower maximum $X_\mathrm{max}$. The ...analysis relies on ${\sim}50,000$
events recorded by the Surface Detector of the Pierre Auger Observatory and a
deep-learning-based reconstruction algorithm. Above energies of 5 EeV, the data
set offers a 10-fold increase in statistics with respect to fluorescence
measurements at the Observatory. After cross-calibration using the Fluorescence
Detector, this enables the first measurement of the evolution of the mean and
the standard deviation of the $X_\mathrm{max}$ distributions up to 100 EeV. Our
findings are threefold:
(1.) The evolution of the mean logarithmic mass towards a heavier composition
with increasing energy can be confirmed and is extended to 100 EeV.
(2.) The evolution of the fluctuations of $X_\mathrm{max}$ towards a heavier
and purer composition with increasing energy can be confirmed with high
statistics. We report a rather heavy composition and small fluctuations in
$X_\mathrm{max}$ at the highest energies.
(3.) We find indications for a characteristic structure beyond a constant
change in the mean logarithmic mass, featuring three breaks that are observed
in proximity to the ankle, instep, and suppression features in the energy
spectrum.
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