Composition at the ``ankle'' measured by the Pierre Auger Observatory: pure or mixed?

Yushkov, A.

doi:10.22323/1.236.0335

Cited by 5 publications

(5 citation statements)

References 20 publications

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“…The BDT response is given in figure 3 (right) for data and for photon and proton QGSJET-II-04 simulations. The discrepancy between the data and the proton simulations is in agreement with the current experimental indications of a composition varying from light to heavier composition in the EeV range [39,54,55] and the muon deficit observed in simulations with respect to the Auger data [56,57]. To identify photons, a cut is defined at the median of the BDT response distribution for photons.…”

Section: Jcap04(2017)009supporting

confidence: 79%

Search for photons with energies above 10¹⁸eV using the hybrid detector of the Pierre Auger Observatory

Aab

Abreu

Aglietta

et al. 2017

J. Cosmol. Astropart. Phys.

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A search for ultra-high energy photons with energies above 1 EeV is performed using nine years of data collected by the Pierre Auger Observatory in hybrid operation mode. An unprecedented separation power between photon and hadron primaries is achieved by combining measurements of the longitudinal air-shower development with the particle content at ground measured by the fluorescence and surface detectors, respectively. Only three photon candidates at energies 1 − 2 EeV are found, which is compatible with the expected hadroninduced background. Upper limits on the integral flux of ultra-high energy photons of 0.027, 0.009, 0.008, 0.008 and 0.007 km −2 sr −1 yr −1 are derived at 95% C.L. for energy thresholds of 1, 2, 3, 5 and 10 EeV. These limits bound the fractions of photons in the all-particle integral flux below 0.1%, 0.15%, 0.33%, 0.85% and 2.7%. For the first time the photon fraction at EeV energies is constrained at the sub-percent level. The improved limits are below the flux of diffuse photons predicted by some astrophysical scenarios for cosmogenic photon production. The new results rule-out the early top-down models − in which ultra-high energy cosmic rays are produced by, e.g., the decay of super-massive particles − and challenge the most recent super-heavy dark matter models.

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Section: Jcap04(2017)009supporting

confidence: 79%

Search for photons with energies above 10¹⁸eV using the hybrid detector of the Pierre Auger Observatory

Aab

Abreu

Aglietta

et al. 2017

J. Cosmol. Astropart. Phys.

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show abstract

“…Measurements of the correlation between the depth of the shower maximum and the number of muons can contribute to the determination of the primary composition. A similar idea is used within the Auger analysis in the energy range of the ankle, finding that the results are in favor of a mixed composition (Yushkov et al 2015). Taken at face value, the Auger results could be interpreted as evidence against the proton dip model (Allard et al 2005.…”

Section: Introductionmentioning

confidence: 82%

Cosmogenic Neutrinos Challenge the Cosmic-Ray Proton Dip Model

Heinze

Boncioli

Bustamante

et al. 2016

ApJ

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The origin and composition of ultra-high-energy cosmic rays (UHECRs) remain a mystery. The proton dip model describes their spectral shape in the energy range above 10 9 GeV by pair production and photohadronic interactions with the cosmic microwave background. The photohadronic interactions also produce cosmogenic neutrinos peaking around 10 9 GeV. We test whether this model is still viable in light of recent UHECR spectrum measurements from the Telescope Array experiment and upper limits on the cosmogenic neutrino flux from IceCube. While two-parameter fits have been already presented, we perform a full scan of the three main physical model parameters: source redshift evolution, injected proton maximal energy, and spectral index. We find qualitatively different conclusions compared to earlier two-parameter fits in the literature: a mild preference for a maximal energy cutoff at the sources instead of the Greisen-Zatsepin-Kuzmin cutoff, hard injection spectra, and strong source evolution. The predicted cosmogenic neutrino flux exceeds the IceCube limit for any parameter combination. As a result, the proton dip model is challenged at more than 95% C.L. This is strong evidence against this model independent of mass composition measurements.

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“…For single nuclear components this correlation is expected to be 0, although for mixed composition, the correlation is negative. For hybrid events with energies of log 10 (E/eV) = 18.5 − 19.0 and zenith angles < 65 • a significant negative correlation was found consistent with a spread of masses σ(lnA) > 1, meaning the composition around the ankle is actually 2017 (2017) mixed [12]. The hypothesis that below 3 EeV, a fraction of protons mainly of extragalactic origin is dominant and that the ankle corresponds to the proton energy loss through e + e − pair production in interactions with the cosmic microwave background (CMB) is then disfavoured.…”

Section: Mass Composition Studiesmentioning

confidence: 80%

The Pierre Auger Observatory status and latest results

Bérat

2017

EPJ Web Conf.

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Abstract. The Pierre Auger Observatory, in Argentina, is the present flagship experiment studying ultrahigh-energy cosmic rays (UHECRs). Facing the challenge due to low cosmic-ray flux at the highest energies, the Observatory has been taking data for more than a decade, reaching an exposure of over 50 000 km 2 sr yr. The combination of a large surface detector array and fluorescence telescopes provides a substantial improvement in energy calibration and extensive air shower measurements, resulting in data of unprecedented quality. Moreover, the installation of a denser subarray has allowed extending the sensitivity to lower energies. Altogether, this contributes to provide important information on key questions in the UHECR field in the energy range from 0.1 EeV up to 100 EeV. A review of main results from the Pierre Auger Observatory is presented with a particular focus on the energy spectrum measurements, the mass composition studies, the arrival directions analyses, the search for neutral cosmic messengers, and the investigation of high-energy hadronic interactions. Despite this large amount of valuable results, the understanding of the nature of UHECRs and of their origin remains an open science case that the Auger collaboration is planning to address with the AugerPrime project to upgrade the Observatory.

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Composition at the ``ankle'' measured by the Pierre Auger Observatory: pure or mixed?

Cited by 5 publications

References 20 publications

Search for photons with energies above 10¹⁸eV using the hybrid detector of the Pierre Auger Observatory

Search for photons with energies above 10¹⁸eV using the hybrid detector of the Pierre Auger Observatory

Cosmogenic Neutrinos Challenge the Cosmic-Ray Proton Dip Model

The Pierre Auger Observatory status and latest results

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Composition at the ``ankle'' measured by the Pierre Auger Observatory: pure or mixed?

Cited by 5 publications

References 20 publications

Search for photons with energies above 1018eV using the hybrid detector of the Pierre Auger Observatory

Search for photons with energies above 1018eV using the hybrid detector of the Pierre Auger Observatory

Cosmogenic Neutrinos Challenge the Cosmic-Ray Proton Dip Model

The Pierre Auger Observatory status and latest results

Contact Info

Product

Resources

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Search for photons with energies above 10¹⁸eV using the hybrid detector of the Pierre Auger Observatory

Search for photons with energies above 10¹⁸eV using the hybrid detector of the Pierre Auger Observatory