267 research outputs found
Cosmic-Ray Anisotropies in Right Ascension Measured by the Pierre Auger Observatory
We present measurements of the large-scale cosmic-ray (CR) anisotropies in R.A., using data collected by the surface detector array of the Pierre Auger Observatory over more than 14 yr. We determine the equatorial dipole component, through a Fourier analysis in R.A. that includes weights for each event so as to account for the main detector-induced systematic effects. For the energies at which the trigger efficiency of the array is small, the east-west method is employed. Besides using the data from the array with detectors separated by 1500 m, we also include data from the smaller but denser subarray of detectors with 750 m separation, which allows us to extend the analysis down to ∼0.03 EeV. The most significant equatorial dipole amplitude obtained is that in the cumulative bin above 8 EeV, %, which is inconsistent with isotropy at the 6σ level. In the bins below 8 EeV, we obtain 99% CL upper bounds on d ⊥ at the level of 1%-3%. At energies below 1 EeV, even though the amplitudes are not significant, the phases determined in most of the bins are not far from the R.A. of the Galactic center, at GC =-94°, suggesting a predominantly Galactic origin for anisotropies at these energies. The reconstructed dipole phases in the energy bins above 4 EeV point instead to R.A. that are almost opposite to the Galactic center one, indicative of an extragalactic CR origin
A Search for Photons with Energies Above 2 × 10 eV Using Hybrid Data from the Low-Energy Extensions of the Pierre Auger Observatory
Ultra-high-energy photons with energies exceeding 10 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 eV range further motivate searches for even higher-energy photons. In this paper, we present a search for photons with energies exceeding 2 × 10 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 and 10 eV
A Search for Photons with Energies above 2 × 1017eV Using Hybrid Data from the Low-Energy Extensions of the Pierre Auger Observatory
Ultra-high-energy photons with energies exceeding 1017 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 1015 eV range further motivate searches for even higher-energy photons. In this paper, we present a search for photons with energies exceeding 2 × 1017 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 1017 and 1018 eV
Searches for Ultra-High-Energy Photons at the Pierre Auger Observatory
The Pierre Auger Observatory, being the largest air-shower experiment in the
world, offers an unprecedented exposure to neutral particles at the highest
energies. Since the start of data taking more than 18 years ago, various
searches for ultra-high-energy (UHE, ) photons have
been performed: either for a diffuse flux of UHE photons, for point sources of
UHE photons or for UHE photons associated with transient events like
gravitational wave events. In the present paper, we summarize these searches
and review the current results obtained using the wealth of data collected by
the Pierre Auger Observatory.Comment: Review article accepted for publication in Universe (special issue on
ultra-high energy photons
Radio Measurements of the Depth of Air-Shower Maximum at the Pierre Auger Observatory
The Auger Engineering Radio Array (AERA), part of the Pierre Auger
Observatory, is currently the largest array of radio antenna stations deployed
for the detection of cosmic rays, spanning an area of km with 153
radio stations. It detects the radio emission of extensive air showers produced
by cosmic rays in the MHz band. Here, we report the AERA measurements
of the depth of the shower maximum (), a probe for mass
composition, at cosmic-ray energies between to eV,
which show agreement with earlier measurements with the fluorescence technique
at the Pierre Auger Observatory. We show advancements in the method for radio
reconstruction by comparison to dedicated sets of CORSIKA/CoREAS
air-shower simulations, including steps of reconstruction-bias identification
and correction, which is of particular importance for irregular or sparse radio
arrays. Using the largest set of radio air-shower measurements to date, we show
the radio resolution as a function of energy, reaching a
resolution better than g cm at the highest energies, demonstrating
that radio measurements are competitive with the established
high-precision fluorescence technique. In addition, we developed a procedure
for performing an extensive data-driven study of systematic uncertainties,
including the effects of acceptance bias, reconstruction bias, and the
investigation of possible residual biases. These results have been
cross-checked with air showers measured independently with both the radio and
fluorescence techniques, a setup unique to the Pierre Auger Observatory.Comment: Submitted to Phys. Rev.
The Pierre Auger Observatory Open Data
The Pierre Auger Collaboration has embraced the concept of open access to
their research data since its foundation, with the aim of giving access to the
widest possible community. A gradual process of release began as early as 2007
when 1% of the cosmic-ray data was made public, along with 100% of the
space-weather information. In February 2021, a portal was released containing
10% of cosmic-ray data collected from 2004 to 2018, during Phase I of the
Observatory. The Portal included detailed documentation about the detection and
reconstruction procedures, analysis codes that can be easily used and modified
and, additionally, visualization tools. Since then the Portal has been updated
and extended. In 2023, a catalog of the 100 highest-energy cosmic-ray events
examined in depth has been included. A specific section dedicated to
educational use has been developed with the expectation that these data will be
explored by a wide and diverse community including professional and
citizen-scientists, and used for educational and outreach initiatives. This
paper describes the context, the spirit and the technical implementation of the
release of data by the largest cosmic-ray detector ever built, and anticipates
its future developments.Comment: 19 pages, 8 figure
Cosmological implications of photon-flux upper limits at ultra-high energies in scenarios of Planckian-interacting massive particles for dark matter
We present a thorough search for signatures that would be suggestive of
super-heavy particles decaying in the Galactic halo, in the data of the
Pierre Auger Observatory. From the lack of signal, we derive upper limits for
different energy thresholds above \,GeV on the expected
secondary by-product fluxes from -particle decay. Assuming that the energy
density of these super-heavy particles matches that of dark matter observed
today, we translate the upper bounds on the particle fluxes into tight
constraints on the couplings governing the decay process as a function of the
particle mass. We show that instanton-induced decay processes allow us to
derive a bound on the reduced coupling constant of gauge interactions in the
dark sector: \alpha_X \alt 0.09, for 10^{9} \alt M_X/\text{GeV} < 10^{19}.
This upper limit on is complementary to the non-observation of
tensor modes in the cosmic microwave background in the context of
Planckian-interacting massive particles for dark matter produced during the
reheating epoch. Viable regions for this scenario to explain dark matter are
delineated in several planes of the multidimensional parameter space that
involves, in addition to and , the Hubble rate at the end of
inflation, the reheating efficiency, and the non-minimal coupling of the Higgs
with curvature.Comment: 15 pages, 8 figures, Accompanying paper of arXiv:2203.0885
Ground observations of a space laser for the assessment of its in-orbit performance
The wind mission Aeolus of the European Space Agency was a groundbreaking
achievement for Earth observation. Between 2018 and 2023, the space-borne lidar
instrument ALADIN onboard the Aeolus satellite measured atmospheric wind
profiles with global coverage which contributed to improving the accuracy of
numerical weather prediction. The precision of the wind observations, however,
declined over the course of the mission due to a progressive loss of the
atmospheric backscatter signal. The analysis of the root cause was supported by
the Pierre Auger Observatory in Argentina whose fluorescence detector
registered the ultraviolet laser pulses emitted from the instrument in space,
thereby offering an estimation of the laser energy at the exit of the
instrument for several days in 2019, 2020 and 2021. The reconstruction of the
laser beam not only allowed for an independent assessment of the Aeolus
performance, but also helped to improve the accuracy in the determination of
the laser beam's ground track on single pulse level. The results presented in
this paper set a precedent for the monitoring of space lasers by ground-based
telescopes and open new possibilities for the calibration of cosmic-ray
observatories.Comment: 10 pages, 10 figure
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