Publisher’s Note: Indications of Proton-Dominated Cosmic-Ray Composition above 1.6 EeV [Phys. Rev. Lett.<b>104</b>, 161101 (2010)]

Abbasi, Rasha; Abu‐Zayyad, T.; Al-Seady, M.; Allen, M.; Amman, J. F.; Anderson, R. J.; Archbold, G.; Belov, K.; Belz, J. W.; Bergman, Douglas; Blake, S. A.; Brusova, O.; Burt, G. W.; Cannon, C.; Cao, Zeyuan; Deng, Weiran; Fedorova, Y.; Finley, C.; Gray, R.; Hanlon, W.; Hoffman, C. M.; Holzscheiter, M. H.; Hughes, G.; Hüntemeyer, P.; Ivanov, D.; Jones, B. F.; Jui, C.; Kim, K.; Kirn, M.; Loh, E. C.; Liu, J.; Lundquist, Jon Paul; Maestas, M. M.; Manago, Naohiro; Marek, Lukáš; Martens, K.; Matthews, J.; Matthews, J. N.; Moore, Sheva; O’Neill, A.; Painter, C. A.; Perera, L.; Reil, K.; Riehle, R.; Roberts, M.; Rodriguez, D.; Sasaki, Nobuya; Schnetzer, S.; Scott, L. M.; Sinnis, G.; Smith, J. D.; Sokolsky, P.; Song, C.; Springer, R. W.; Stokes, Ben; Stratton, S. R.; Thomas, S. B.; Thomas, J. R.; Thomson, G. B.; Tupa, D.; Zech, A.; Zhang, X.

doi:10.1103/physrevlett.104.199902

Cited by 65 publications

(83 citation statements)

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“…Considering the data from Yakutsk and Tunka one obtains lnA xg ≃ 2.6 to 1.4, so that the average extragalactic CR mass ranges from that of N (for Sibyll) to that of He (for QGSJet). This is in tension with measurements in the EeV range by Auger [22] and HiRes [40] that find that for the energies 0.3 to 1 EeV the average composition should not be heavier than He. Considering Auger composition data one infers that lnA xg ≃ 1.3 to 0, consistent with an average mass between that of He (for Sibyll) and H (for QGSJet).…”

Section: Discussioncontrasting

confidence: 69%

“…The Galactic CRs include almost all known nuclear elements, with a composition having some similarities with the abundances found in the solar system although they also present some clear differences (such as the abundances of the spallation products mentioned before or those that may be associated to the contributions to the CR fluxes coming from different types of supernovae, etc.). The most abundant elements are H, 4 He, light nuclei such as 12 C, 14 N and 16 O, intermediate mass nuclei such as 20 Ne, 24 Mg, 28 Si or 32 S or heavier nuclei such as 36 Ar, 40 Ca and specially 56 Fe. We will hence adopt for simplicity five representative mass components, A = H, He, N, Si and Fe, to describe the Galactic CR fluxes.…”

Section: Spectrum Of the Galactic And Extragalactic Componentsmentioning

confidence: 99%

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A scenario for the Galactic cosmic rays between the knee and the second-knee

Mollerach¹,

Roulet

2019

J. Cosmol. Astropart. Phys.

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We perform a fit to measurements of the cosmic ray spectrum in the energy range between 10 15 eV and 10 18 eV using data from the TALE, Tunka and Auger experiments. We also fit the data on the depth of shower maximum, Xmax, from Tunka and Yakutsk or from Auger to constrain the cosmic ray composition. We consider a Galactic component that is a mixture of five representative nuclear species (H, He, N, Si and Fe), for which we adopt rigidity dependent broken power-law spectra, and we allow for an extragalactic component which becomes strongly suppressed for decreasing energies. The relative abundances of the Galactic components at 10 15 eV are taken to be comparable to those determined by direct measurements at 10 13 eV. The main features of the spectrum and of the composition are reproduced in these scenarios. The spectral knee results from the break of the H spectrum at E k ≃ 3 × 10 15 eV, although it is broadened by the comparable contribution from He which has a break at about 6×10 15 eV. The low-energy ankle at E la ≃ 2×10 16 eV coincides with the strong suppression of the H and He Galactic components and the increasing relative contribution of the heavier ones, but the observed hardening of the spectrum at this energy turns out to result from the growing contribution of the extragalactic component. The second-knee at E sk ≃ 26E k ≃ 8 × 10 16 eV is associated with the steepening of the Galactic Fe component. The transition to the regime in which the total cosmic ray flux is dominated by the extragalactic component takes place at an energy of about 10 17 eV. The parameters of the fit depend on the specific Xmax dataset that is considered, with the Yakutsk and Tunka data leading to a suppression of the light components being steeper beyond the knee so as to allow a faster growth of the average mass around the low-energy ankle. The results also depend on the hadronic model that is used to interpret Xmax measurements and we compare the parameters obtained with Sibyll 2.3, EPOS-LHC and QGSJET II-04. The impact of the possible existence of a maximum rigidity cutoff in the Galactic components is also discussed.

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Section: Discussioncontrasting

confidence: 69%

Section: Spectrum Of the Galactic And Extragalactic Componentsmentioning

confidence: 99%

A scenario for the Galactic cosmic rays between the knee and the second-knee

Mollerach¹,

Roulet

2019

J. Cosmol. Astropart. Phys.

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“…4 shows the UHECR proton flux from ϕ 7 and ϕ 8 for zero evolution, as often assumed for BL Lacs, or cosmic star formation rate [76][77][78] evolution. These fall below the data [79][80][81][82], though ϕ 8 is close at > ∼ 10 18 eV where the composition is light [83][84][85]. Fewer pions per neutron would raise the flux [48], though saturation would leave no room for UHECR mechanisms besides neutron escape from IceCube sources.…”

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confidence: 68%

Multi-PeV Signals from a New Astrophysical Neutrino Flux beyond the Glashow Resonance

Kistler

Laha

2018

Phys. Rev. Lett.

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The IceCube neutrino discovery was punctuated by three showers with E_{ν}≈1-2 PeV. Interest is intense in possible fluxes at higher energies, though a deficit of E_{ν}≈6 PeV Glashow resonance events implies a spectrum that is soft and/or cutoff below ∼few PeV. However, IceCube recently reported a through-going track depositing 2.6±0.3 PeV. A muon depositing so much energy can imply E_{ν_{μ}}≳10 PeV. Alternatively, we find a tau can deposit this much energy, requiring E_{ν_{τ}}∼10× higher. We show that extending soft spectral fits from TeV-PeV data is unlikely to yield such an event, while an ∼E_{ν}^{-2} flux predicts excessive Glashow events. These instead hint at a new flux, with the hierarchy of ν_{μ} and ν_{τ} energies implying astrophysical neutrinos at E_{ν}∼100 PeV if a tau. We address implications for ultrahigh-energy cosmic-ray and neutrino origins.

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“…This suggests that the UHECR composition transitions from being dominated by protons below the ankle to being dominated by heavier nuclei with average masses similar to Si or Fe at ∼5 × 10 19 eV (see also Glushkov et al 2008). We caution, however, that HiRes has not verified this finding (Abbasi et al 2005(Abbasi et al , 2010. 2 The UHECR composition measured by Auger is puzzling.…”

Section: Introductionmentioning

confidence: 88%

Heavy nuclei synthesized in gamma-ray burst outflows as the source of ultrahigh energy cosmic rays

Metzger

Giannios

Horiuchi

2011

Monthly Notices of the Royal Astronomical Society

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Recent measurements by the Pierre Auger Observatory suggest that the composition of ultrahigh energy cosmic rays (UHECRs) becomes dominated by heavy nuclei at high energies. However, until now there has been no astrophysical motivation for considering a source highly enriched in heavy elements. Here we demonstrate that the outflows from gamma‐ray bursts (GRBs) may indeed be composed primarily of nuclei with masses A∼ 40–200, which are synthesized as hot material expands away from the central engine. In particular, if the jet is magnetically dominated (rather than a thermally driven fireball) its low entropy enables heavy elements to form efficiently. Adopting the millisecond protomagnetar model for the GRB central engine, we show that heavy nuclei both are synthesized in protomagnetar winds and can in principle be accelerated to energies ≳1020 eV in the shocks or regions of magnetic reconnection that are responsible for powering the GRB. Similar results may apply to accretion‐powered GRB models if the jet originates from a magnetized disc wind. Depending on the precise distribution of nuclei synthesized, we predict that the average primary mass may continue to increase beyond Fe group elements at the highest energies, possibly reaching the A≈ 90 (zirconium), A≈ 130 (tellurium) or even A≈ 195 (platinum) peaks. Future measurements of the UHECR composition at energies ≳1020 eV can thus confirm or constrain our model and, potentially, probe the nature of GRB outflows. The longer attenuation length of ultra‐heavy nuclei through the extragalactic background light greatly expands the volume of accessible sources and alleviates the energetic constraints on GRBs as the source of UHECRs.

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Publisher’s Note: Indications of Proton-Dominated Cosmic-Ray Composition above 1.6 EeV [Phys. Rev. Lett.104, 161101 (2010)]

Cited by 65 publications

References 0 publications

A scenario for the Galactic cosmic rays between the knee and the second-knee

A scenario for the Galactic cosmic rays between the knee and the second-knee

Multi-PeV Signals from a New Astrophysical Neutrino Flux beyond the Glashow Resonance

Heavy nuclei synthesized in gamma-ray burst outflows as the source of ultrahigh energy cosmic rays

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