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.
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.
We present the GIGAS (Gigahertz Identification of Giant Air Shower) microwave radio sensor arrays of the EASIER project (Extensive Air Shower Identification with Electron Radiometers), deployed at ...the site of the Pierre Auger cosmic ray observatory. The aim of these novel arrays is to probe the intensity of the molecular bremsstrahlung radiation expected from the development of the extensive air showers produced by the interaction of ultra high energy cosmic rays in the atmosphere. In the designed setup, the sensors are embedded within the surface detector array of the Pierre Auger observatory allowing us to use the particle signals at ground level to trigger the radio system. A series of seven, then 61 sensors have been deployed in the C-band, followed by a new series of 14 higher sensitivity ones in the C-band and the L-band. The design, the operation, the calibration and the sensitivity to extensive air showers of these arrays are described in this paper.
We present a measurement of the momentum spectra of π±, K±, p±, Λ, ¯Λ, and K0S produced in interactions of negatively charged pions with carbon nuclei at beam momenta of 158 and 350 GeV/c. The total ...production cross sections are measured as well. The data were collected with the large-acceptance spectrometer of the fixed target experiment NA61/SHINE at the CERN SPS. The obtained double-differential p−pT spectra provide a unique reference dataset with unprecedented precision and large phase-space coverage to tune models used for the simulation of particle production in extensive air showers in which pions are the most numerous projectiles.
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.
Familial platelet disorder with predisposition to acute myelogenous leukaemia (FPD/AML, MIM 601399) is an autosomal dominant disorder characterized by qualitative and quantitative platelet defects, ...and propensity to develop acute myelogenous leukaemia (AML). Informative recombination events in 6 FPD/AML pedigrees with evidence of linkage to markers on chromosome 21q identified an 880-kb interval containing the disease gene. Mutational analysis of regional candidate genes showed nonsense mutations or intragenic deletion of one allele of the haematopoietic transcription factor CBFA2 (formerly AML1) that co-segregated with the disease in four FPD/AML pedigrees. We identified heterozygous CBFA2 missense mutations that co-segregated with the disease in the remaining two FPD/AML pedigrees at phylogenetically conserved amino acids R166 and R201, respectively. Analysis of bone marrow or peripheral blood cells from affected FPD/AML individuals showed a decrement in megakaryocyte colony formation, demonstrating that CBFA2 dosage affects megakaryopoiesis. Our findings support a model for FPD/AML in which haploinsufficiency of CBFA2 causes an autosomal dominant congenital platelet defect and predisposes to the acquisition of additional mutations that cause leukaemia.
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.
We present measurements of
ρ
0
,
ω
and K
∗
0
spectra in
π
-
+
C production interactions at 158
GeV
/
c
and
ρ
0
spectra at 350
GeV
/
c
using the NA61/SHINE spectrometer at the CERN SPS. Spectra are ...presented as a function of the Feynman’s variable
x
F
in the range
0
<
x
F
<
1
and
0
<
x
F
<
0.5
for 158 and 350
GeV
/
c
respectively. Furthermore, we show comparisons with previous measurements and predictions of several hadronic interaction models. These measurements are essential for a better understanding of hadronic shower development and for improving the modeling of cosmic ray air showers.
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.
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