Measurement of the cosmic-ray energy spectrum above $2.5\times 10^{18}$ eV using the Pierre Auger Observatory

Abstract

We report a measurement of the energy spectrum of cosmic rays for energies above $2.5\times 10^{18}$eV based on 215,030 events recorded with zenith angles below $60^{\circ }$. 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 $5\times 10^{19}$eV. The principal conclusions are: (1) The flattening of the spectrum near $5\times 10^{18}$eV, the so-called "ankle", is confirmed. (2) The steepening of the spectrum at around $5\times 10^{19}$eV is confirmed. (3) A new feature has been identified in the spectrum: in the region above the ankle the spectral index $\gamma$ of the particle flux ($\propto E^{-\gamma }$) changes from $2.51\pm 0.03(stat.)\pm 0.05(sys.)$ to $3.05\pm 0.05(stat.)\pm 0.10(sys.)$ before changing sharply to $5.1\pm 0.3(stat.)\pm 0.1(sys.)$ above $5\times 10^{19}$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 $8\times 10^{18}$eV.

Published version; 16 figures, 6 table

References in corpus (10)

• Observation of a Large-scale Anisotropy in the Arrival Directions of Cosmic Rays above $8\times 10^{18}$ eV
• Depth of Maximum of Air-Shower Profiles at the Pierre Auger Observatory: Measurements at Energies above 10^17.8 eV
• The Cosmic Ray Energy Spectrum Observed with the Surface Detector of the Telescope Array Experiment
• Features of the energy spectrum of cosmic rays above $2.5\times 10^{18}$ eV using the Pierre Auger Observatory
• Reconstruction of Longitudinal Profiles of Ultra-High Energy Cosmic Ray Showers from Fluorescence and Cherenkov Light Measurements
• The Optimum Distance at which to Determine the Size of a Giant Air Shower
• Cosmic Rays from the Ankle to the Cut-Off
• Spectral features in the cosmic ray fluxes
• Impact of atmospheric effects on the energy reconstruction of air showers observed by the surface detectors of the Pierre Auger Observatory
• Normalization of the extragalactic background light from high-energy gamma-ray observations

Cited by in corpus (86)

• Features of the energy spectrum of cosmic rays above $2.5\times 10^{18}$ eV using the Pierre Auger Observatory
• The Muon Puzzle in cosmic-ray induced air showers and its connection to the Large Hadron Collider
• The energy spectrum of cosmic rays beyond the turn-down around $10^{17}$ eV as measured with the surface detector of the Pierre Auger Observatory
• Ultra-High-Energy Cosmic Rays: The Intersection of the Cosmic and Energy Frontiers
• Arrival Directions of Cosmic Rays above 32 EeV from Phase One of the Pierre Auger Observatory
• Measurement of the fluctuations in the number of muons in extensive air showers with the Pierre Auger Observatory
• Constraining the sources of ultra-high-energy cosmic rays across and above the ankle with the spectrum and composition data measured at the Pierre Auger Observatory
• Cosmic Ray Extremely Distributed Observatory
• The Imprint of Large Scale Structure on the Ultra-High-Energy Cosmic Ray Sky
• Inference of cosmic-ray source properties by conditional invertible neural networks
• Constraining models for the origin of ultra-high-energy cosmic rays with a novel combined analysis of arrival directions, spectrum, and composition data measured at the Pierre Auger Observatory
• Testing effects of Lorentz invariance violation in the propagation of astroparticles with the Pierre Auger Observatory
• Observation of night-time emissions of the Earth in the near UV range from the International Space Station with the Mini-EUSO detector
• Revisiting ultrahigh-energy constraints on decaying super-heavy dark matter
• EUSO-SPB1 Mission and Science
• Reconstruction of Events Recorded with the Surface Detector of the Pierre Auger Observatory
• Hunting super-heavy dark matter with ultra-high energy photons
• What can be learnt from UHECR anisotropies observations? Paper I : large-scale anisotropies and composition features
• Extraction of the Muon Signals Recorded with the Surface Detector of the Pierre Auger Observatory Using Recurrent Neural Networks
• Testing Hadronic-Model Predictions of Depth of Maximum of Air-Shower Profiles and Ground-Particle Signals using Hybrid Data of the Pierre Auger Observatory
• Design and Initial Performance of the Prototype for the BEACON Instrument for Detection of Ultrahigh Energy Particles
• Curious case of the maximum rigidity distribution of cosmic-ray accelerators
• Science and mission status of EUSO-SPB2
• Limits to gauge coupling in the dark sector set by the non-observation of instanton-induced decay of Super-Heavy Dark Matter in the Pierre Auger Observatory data
• Testing hadronic and photo-hadronic interactions as responsible for UHECR and neutrino fluxes from Starburst Galaxies
• Large-scale cosmic ray anisotropies with 19 years of data from the Pierre Auger Observatory
• The UHECR dipole and quadrupole in the latest data from the original Auger and TA surface detectors
• Constraints on UHECR sources and extragalactic magnetic fields from directional anisotropies
• Expected Performance of the EUSO-SPB2 Fluorescence Telescope
• Energetics of ultrahigh-energy cosmic-ray nuclei
• Constraints on the proton fraction of cosmic rays at the highest energies and the consequences for cosmogenic neutrinos and photons
• Nuclear and electromagnetic cascades induced by ultrahigh-energy cosmic rays in radio galaxies: implications for Centaurus A
• Ultra-High-Energy Cosmic Rays Accelerated by Magnetically Dominated Turbulence
• Stellar Mass and Star Formation Rate within a Billion Light-Years
• Development of a cosmic ray oriented trigger for the fluorescence telescope on EUSO-SPB2
• Measurement of the Depth of Maximum of Air-Shower Profiles with energies between $10^{18.5}$ and $10^{20}$ eV using the Surface Detector of the Pierre Auger Observatory and Deep Learning
• Ultra High Energy Cosmic Ray Source Models: Successes, Challenges and General Predictions
• Further Evidence for an Increase of the Mean Mass of the Highest-Energy Cosmic-Rays with Energy
• The EUSO-SPB2 Fluorescence Telescope for the Detection of Ultra-High Energy Cosmic Rays
• Differences Between the Pierre Auger Observatory and Telescope Array Spectra: Systematic Effects or Indication of a Local Source of Ultra-High-Energy Cosmic Rays?
• Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review
• Exploring black holes as particle accelerators: hoop-radius, target particles and escaping conditions
• Developments and results in the context of the JEM-EUSO program obtained with the ESAF Simulation and Analysis Framework
• Modeling Strangeness Enhancements to resolve the Muon Excess in Cosmic Ray Extensive Air Shower Data
• Propagation and Fluxes of Ultra High Energy Cosmic Rays in f(R) Gravity Theory
• Probing superheavy dark matter through lunar radio observations of ultrahigh-energy neutrinos and the impacts of neutrino cascades
• EUSO-SPB2 Fluorescence Telescope in-flight performance and preliminary results
• The spectra and composition of Ultra High Energy Cosmic Rays and the measurement of the proton-air cross section
• The science of ultra-high energy cosmic rays after more than 15 years of operation of the Pierre Auger Observatory
• Ultrahigh-energy dipole and beyond
• The Radio Detector of the Pierre Auger Observatory -- status and expected performance
• Constraints on the hosts of UHECR accelerators
• Anisotropies of Diffusive Ultra-high Energy Cosmic Rays in $f(R)$ Gravity Theory
• A cosmic Zevatron based on cyclotron auto-resonance
• Impact of the finite life-time of UHECR sources
• Search for a diffuse flux of photons with energies above tens of PeV at the Pierre Auger Observatory
• Densities of States and the CKN Bound
• Learning the Composition of Ultra High Energy Cosmic Rays
• The large-scale anisotropy and flux (de-)magnification of ultra-high-energy cosmic rays in the Galactic magnetic field
• Nearby active galactic nuclei and starburst galaxies as sources of the measured UHECRs anisotropy signal
• The distribution of ultra-high-energy cosmic rays along the supergalactic plane measured at the Pierre Auger Observatory
• A search for the anomalous events detected by ANITA using the Pierre Auger Observatory
• Ultraheavy Ultrahigh-Energy Cosmic Rays
• Magnetic Suppression of Cosmic Rays' Flux in $\mathbf{f}(\mathbf{R})$ and $\mathbf{f}(\mathbf{Q})$ Theories of Gravity
• Abnormal threshold behaviors of photo-pion production off the proton in the GZK region
• Ultra-high-energy Cosmic Ray Sources can be Gamma-ray Dim
• The Pierre Auger Observatory Open Data
• A Heavy-Metal Scenario of Ultra-High-Energy Cosmic Rays
• Effects of large-scale magnetic fields on the observed composition of ultra high-energy cosmic rays
• Evaluations of uncertainties in simulations of propagation of ultrahigh-energy cosmic-ray nuclei derived from microscopic nuclear models
• A relook at the GZK Neutrino-Photon Connection: Impact of Extra-galactic Radio Background & UHECR properties
• Relativistic dust grains: a new subject of research with orbital fluorescence detectors
• Bilateral constraints on proton Lorentz violation effects
• A Study of Modified Characteristics of Hadronic Interactions
• Analysing Ultra High Energy Cosmic Rays' Anisotropy in $\mathbf{f}(\mathbf{R},\mathbf{T})$ Gravity Theory
• Cosmic ray mass composition measurement in the energy range from $10^{16.5}$ eV to $10^{18.5}$ eV observed with the TALE hybrid detector
• Radio Detection of Ultra-high Energy Cosmic Rays with Low Lunar Orbiting SmallSats
• Testing Model Predictions of Depth of Air-Shower Maximum and Signals in Surface Detectors using Hybrid Data of the Pierre Auger Observatory
• Energy evolution of cosmic-ray mass and intensity measured by the Pierre Auger Observatory
• Explaining the UHECR spectrum, composition and large-scale anisotropies with radio galaxies
• Modelling Cosmic Rays Flux with Pierre Auger and Telescope Array Data in $\mathbf{f}(\mathbf{R})$ and $\mathbf{f}(\mathbf{Q})$ Theories of Gravity
• An Improved Method of Estimating the Uncertainty of Air-Shower Size at Ultra-High Energies
• Ultra-high energy cosmic rays with UFA-15 source model in Bumblebee gravity theory
• The Scintillator Surface Detector of the Pierre Auger Observatory
• POEMMA-Balloon with Radio: A multi-messenger, multi-detector balloon payload
• Joint constraint on the propagation origin of the cosmic-ray spectral knee from energy spectrum and anisotropy observations