DISCREPANT HARDENING OBSERVED IN COSMIC-RAY ELEMENTAL SPECTRA

By H. Ahn, P. Allison, M. G. Bagliesi, J. Beatty, G. Bigongiari, J. Childers, N. Conklin, S. Coutu, M. DuVernois, O. Ganel and 22 more. 2010

321 citations recorded by the source corpus.

The balloon-borne Cosmic Ray Energetics And Mass experiment launched five times from Antarctica has achieved a cumulative flight duration of about 156 days above 99.5% of the atmosphere. The instrument is configured with complementary and redundant particle detectors designed to extend direct measurements of cosmic-ray composition to the highest energies practical with balloon flights. All elements from protons to iron nuclei are separated with excellent charge resolution. Here, we report results from the first two flights of ∼70 days, which indicate hardening of the elemental spectra above ∼200 GeV/nucleon and a spectral difference between the two most abundant species, protons and helium nuclei. These results challenge the view that cosmic-ray spectra are simple power laws below the so-called knee at ∼1015 eV. This discrepant hardening may result from a relatively nearby source, or it could represent spectral concavity caused by interactions of cosmic rays with the accelerating shock. Other possible explanations should also be investigated.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/fa620f6f299c51e017914b5e56f6869186c3e901

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. P. Blasi
2. E. Amato
3. E. Seo
4. P. Serpico
5. Aurélien Barrau
6. Angela V. Olinto
7. L. Derome
8. Kumiko Kotera

In Nuclear and High Energy Physics

1. E. Amato
2. P. Blasi
3. Kumiko Kotera
4. Angela V. Olinto
5. E. Seo
6. P. Serpico
7. L. Derome
8. A. Putze

Citations in the corpus

• Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. II: anisotropy (2011, result): “The case of fast diffusion also leads in general to negligible spallation of nuclei, so that the Helium spectrum at Earth is roughly parallel to that of protons, in contradiction with recent CREAM [10] and PAMELA [11] data that suggest a harder He spectrum above TeV energies.”
• Astrophysical models for the origin of the positron (2011, background): “1The recent indication by CREAM [22] and PAMELA [23] that Helium spectra are about ∼ 0.”
• The Astrophysics of Ultrahigh-Energy Cosmic Rays (2011, methodology): “Composition measurements can be made directly up to energies of ∼ 100 TeV with space-based experiments (see, e.g., Ahn et al. 2010).”
• Proton and Helium Spectra from the CREAM-III Flight (2017, background): “Elemental spectra from the first two CREAM flights were reported in Ahn et al. (2007, 2009, 2010) and Yoon et al. (2011) [2, 3, 4, 5].”
• The origin of galactic cosmic rays (2013, unknown): “The slopes of protons and helium spectra at high energies as measured by PAMELA appear to be in agreement with those measured by the CREAM experiment (Ahn et al. 2010) at supra-TeV energies.”
• COSMIC-RAY PROTON AND HELIUM SPECTRA FROM THE FIRST CREAM FLIGHT (2011, methodology): “The measured proton fluxes from 2.5 TeV to 250 TeV and helium fluxes from 630 GeV nucleon−1 to 63 TeV nucleon−1 at the top of the atmosphere are given in Tables 2 and 3, while previously reported results in the paper by Ahn et al. (2010) are presented in a plot.”
• Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. I: spectrum and chemical composition (2011, methodology): “Two important observational findings recently appeared in the literature on cosmic rays: first, the sharp hardening found by ATIC-2 [34], CREAM [17] and PAMELA [35] in both the – 20 – proton and He spectra at ∼ 200 GeV/nucleon; second, the fact that the He spectrum above this energy appears to be ha”