University of Oulu

Koldobskiy, S., Neronov, A., & Semikoz, D. (2021). Pion decay model of the Tibet- ASγ PeV gamma-ray signal. Physical Review D, 104(4).

Pion decay model of the Tibet-ASγ PeV gamma-ray signal

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Author: Koldobskiy, Sergey1,2; Neronov, Andrii3,4; Semikoz, Dmitri3,5,1
Organizations: 1National Research Nuclear University MEPhI, 115409 Moscow, Russia
2University of Oulu, 90570 Oulu, Finland
3Université de Paris, CNRS, Astroparticule et Cosmologie, F-75006 Paris, France
4Astronomy Department, University of Geneva, Chemin d’Ecogia 16, 1290 Versoix, Switzerland
5Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 117312, Russia
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.5 MB)
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Language: English
Published: American Physical Society, 2021
Publish Date: 2021-08-25


The Tibet-ASγ Collaboration has recently reported a measurement of diffuse γ-ray flux from the outer Galactic disk in the energy range reaching PeV. We complement this measurement with the Fermi/LAT measurement of the diffuse flux from the same sky region and study the pion decay model of the combined Fermi/LAT + Tibet-ASγ spectrum. We find that within such a model the average cosmic-ray spectrum in the outer Galactic disk has the same characteristic features as the local cosmic-ray spectrum. In particular, it experiences a hardening at several hundred GV rigidity and a knee feature in the PV rigidity range. The slope of the average cosmic-ray spectrum above the break is close to the locally observed slope of the helium spectrum γ ≃ 2.5, but is harder than the slope of the local proton spectrum in the same rigidity range. Although the combination of Fermi/LAT and Tibet-ASγ data points to the presence of the knee in the average cosmic-ray spectrum, the quality of the data is not yet sufficient for the study of knee shape and cosmic-ray composition.

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Series: Physical review. D
ISSN: 2470-0010
ISSN-E: 2470-0029
ISSN-L: 2470-0010
Volume: 104
Issue: 4
Article number: 043010
DOI: 10.1103/PhysRevD.104.043010
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: The work of A. N. and D. S. was supported by the Ministry of science and higher education of Russian Federation under the Contract No. 075-15-2020-778 in the framework of the large scientific projects program within the national project “Science”.
Copyright information: © 2021 American Physical Society.