We show, for the first time, radio measurements of the depth of shower maximum (X_{max}) of air showers induced by cosmic rays that are compared to measurements of the established fluorescence method ...at the same location. Using measurements at the Pierre Auger Observatory we show full compatibility between our radio and the previously published fluorescence dataset, and between a subset of air showers observed simultaneously with both radio and fluorescence techniques, a measurement setup unique to the Pierre Auger Observatory. Furthermore, we show radio X_{max} resolution as a function of energy and demonstrate the ability to make competitive high-resolution X_{max} measurements with even a sparse radio array. With this, we show that the radio technique is capable of cosmic-ray mass composition studies, both at Auger and at other experiments.
We test the predictions of hadronic interaction models regarding the depth of maximum of air-shower profiles, X max , and ground-particle signals in water-Cherenkov detectors at 1000 m from the ...shower core, S ( 1000 ) , using the data from the fluorescence and surface detectors of the Pierre Auger Observatory. The test consists of fitting the measured two-dimensional ( S ( 1000 ) , X max ) distributions using templates for simulated air showers produced with hadronic interaction models pos-, et--04, 2.3d and leaving the scales of predicted X max and the signals from hadronic component at ground as free-fit parameters. The method relies on the assumption that the mass composition remains the same at all zenith angles, while the longitudinal shower development and attenuation of ground signal depend on the mass composition in a correlated way. The analysis was applied to 2239 events detected by both the fluorescence and surface detectors of the Pierre Auger Observatory with energies between 10 18.5 eV to 10 19.0 eV and zenith angles below 60°. We found, that within the assumptions of the method, the best description of the data is achieved if the predictions of the hadronic interaction models are shifted to deeper X max values and larger hadronic signals at all zenith angles. Given the magnitude of the shifts and the data sample size, the statistical significance of the improvement of data description using the modifications considered in the paper is larger than 5 σ even for any linear combination of experimental systematic uncertainties. Published by the American Physical Society 2024
Abstract
Lorentz invariance violation (LIV) is often described by dispersion relations of the form
E
i
2
=
m
i
2
+
p
i
2
+δ
i,n
E
2+n
with delta different based on particle type
i
, with energy
E
, ...momentum
p
and rest mass
m
. Kinematics and energy thresholds of interactions are modified once the LIV terms become comparable to the squared masses of the particles involved. Thus, the strongest constraints on the LIV coefficients δ
i,n
tend to come from the highest energies. At sufficiently high energies, photons produced by cosmic ray interactions as they propagate through the Universe could be subluminal and unattenuated over cosmological distances. Cosmic ray interactions can also be modified and lead to detectable fingerprints in the energy spectrum and mass composition observed on Earth. The data collected at the Pierre Auger Observatory are therefore possibly sensitive to both the electromagnetic and hadronic sectors of LIV. In this article, we explore these two sectors by comparing the energy spectrum and the composition of cosmic rays and the upper limits on the photon flux from the Pierre Auger Observatory with simulations including LIV. Constraints on LIV parameters depend strongly on the mass composition of cosmic rays at the highest energies. For the electromagnetic sector, while no constraints can be obtained in the absence of protons beyond 10
19
eV, we obtain δ
γ,0
> -10
-21
, δ
γ,1
> -10
-40
eV
-1
and δ
γ,2
> -10
-58
eV
-2
in the case of a subdominant proton component up to 10
20
eV. For the hadronic sector, we study the best description of the data as a function of LIV coefficients and we derive constraints in the hadronic sector such as δ
had,0
< 10
-19
, δ
had,1
< 10
-38
eV
-1
and δ
had,2
< 10
-57
eV
-2
at 5σ CL.
Abstract
The combined fit of the measured energy spectrum and shower maximum depth distributions of ultra-high-energy cosmic rays is known to constrain the parameters of astrophysical models with ...homogeneous source distributions. Studies of the distribution of the cosmic-ray arrival directions show a better agreement with models in which a fraction of the flux is non-isotropic and associated with the nearby radio galaxy Centaurus A or with catalogs such as that of starburst galaxies.
Here, we present a novel combination of both analyses by a simultaneous fit of arrival directions, energy spectrum, and composition data measured at the Pierre Auger Observatory. The model takes into account a rigidity-dependent magnetic field blurring and an energy-dependent evolution of the catalog contribution shaped by interactions during propagation.
We find that a model containing a flux contribution from the starburst galaxy catalog of around 20% at 40 EeV with a magnetic field blurring of around 20° for a rigidity of 10 EV provides a fair simultaneous description of all three observables.
The starburst galaxy model is favored with a significance of 4.5σ (considering experimental systematic effects) compared to a reference model with only homogeneously distributed background sources. By investigating a scenario with Centaurus A as a single source in combination with the homogeneous background, we confirm that this region of the sky provides the dominant contribution to the observed anisotropy signal. Models containing a catalog of jetted active galactic nuclei whose flux scales with the γ-ray emission are, however, disfavored as they cannot adequately describe the measured arrival directions.
We use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above 1019 eV. Photons in the zenith angle range from 30∘ to 60∘ can be ...identified in the overwhelming background of showers initiated by charged cosmic rays through the broader time structure of the signals induced in the water-Cherenkov detectors of the array and the steeper lateral distribution of shower particles reaching ground. Applying the search method to data collected between January 2004 and June 2020, upper limits at 95% CL are set to an E-2 diffuse flux of ultra-high energy photons above 1019 eV, 2 × 1019 eV and 4 × 1019 eV amounting to 2.11 × 10-3, 3.12 × 10-4 and 1.72 × 10-4 km-2 sr-1 yr-1, respectively. While the sensitivity of the present search around 2 × 1019 eV approaches expectations of cosmogenic photon fluxes in the case of a pure-proton composition, it is one order of magnitude above those from more realistic mixed-composition models. The inferred limits have also implications for the search of super-heavy dark matter that are discussed and illustrated.
Cuboidal ceria nanoparticles have been used to enhance the rate of decomposition of carbonized sucrose. Pure sucrose has been subjected to pyrolysis under the nitrogen atmosphere at 500 °C to obtain ...carbonized sucrose. Ceria nanocuboids have been prepared by hydrothermal method. The transmission electron microscopy analysis shows formation of cuboids with sizes ranging from 10 to 40 nm. The X-ray diffraction and selected area electron diffraction studies show FCC structure of ceria. The line profile analysis of atomic rows on the surface of a typical ceria nanocuboid imaged along zone axis has been presented. Temperature-dependent decomposition of carbonized sucrose has been studied by treating known amount of the material in a Thermogravimetric Analyzer (TGA). The weight loss observed in the case of pure carbonized sucrose and the one mixed with about 9% ceria nanocuboids, have been analyzed using FTIR spectra of the samples before and after TG treatment. Enhanced weight-loss, in the case of ceria mixed carbonized sucrose, has been explained as due to redox ability of ceria, owing to active {100} and {110} facets.
Addition of measured amounts of fillers into a polymer matrix is expected to improve the desired properties of the composites. Also the ease of processability of the matrix and reinforcement is ...always desired. Use of powder fillers in the polymer matrix at ambient conditions would make the processing much easier. This will help in in situ applications. In the present work, polymer–matrix composites are prepared with polystyrene as the matrix using metal (copper/aluminum/steel) and ceramic (alumina) fillers at ambient conditions. The composites with metallic and ceramic fillers in the ratio of 50:25:25 wt% (polymer:filler 1:filler 2) designated as three-phase composites were investigated for tribological applications. Both copper and aluminum fillers were considered for comparison in terms of their contribution to tribological behavior because of their thermal conductivity, specific heat and density.
Polystyrene is filled with metal powder (copper, aluminum or steel) and alumina in equal proportion and subjected to wear and friction tests. The polymer steel–ceramic composite has the least with the other two composites having almost the same values of friction coefficient. The polymer aluminum–ceramic composite has the least wear at all operating conditions. Polymer aluminum–ceramic composite was found to have better wear behavior among the three-phase composites. This may be attributed to the favorable value of density of aluminum, moderate thermal conductivity and excellent specific heat.
The search for correlations between secondary cosmic ray detection rates and seismic effects has long been a subject of investigation motivated by the hope of identifying a new precursor type that ...could feed a global early warning system against earthquakes. Here we show for the first time that the average variation of the cosmic ray detection rates correlates with the global seismic activity to be observed with a time lag of approximately two weeks, and that the significance of the effect varies with a periodicity resembling the undecenal solar cycle, with a shift in phase of around three years, exceeding 6 σ at local maxima. The precursor characteristics of the observed correlations point to a pioneer perspective of an early warning system against earthquakes.
Variations of secondary cosmic ray detection rates are periodically correlated with future global earthquake magnitude sum.
•The local changes of the cosmic ray flux correlate with the global seismic activity.•The cosmic signal correlates with the future seismic activity.•The effect lasts a few years and occurs with periodicity similar to the solar cycle.
PDF
