Constraining the position of the knee in the galactic cosmic ray spectrum with ultra-high-energy diffuse $γ$-rays

Abstract

The diffuse γ-ray was measured up to 957 TeV by the Tibet-ASγ experiment. Presuming it is produced by the hadronic interaction between cosmic ray nuclei and the interstellar medium, it requires that the cosmic ray nuclei should be accelerated well beyond PeV energies. However, measurements of the spectrum of proton and Helium by a few experiments show break below PeV. To solve this apparent discrepancy, we propose in this work that a new structure of cosmic rays may exist beyond PeV, which can contribute to the highest energy diffuse γ rays. This additional component may serve as another population of Galactic cosmic ray accelerators, and can contribute to the cosmic ray fluxes beyond the second knee. Future measurements of the energy spectra of different nuclei species may test the existence of this new component.

Galactic gamma-ray and neutrino emission from interacting cosmic-ray nuclei

“…We note that in finalising this work, a number of pre-prints related to the results of Amenomori et al ( 2021) have been made public (Dzhatdoev 2021;Liu & Wang 2021;Qiao et al 2021;Fang & Murase 2021;Koldobskiy et al 2021;Esmaili & Serpico 2021;Nath Maity et al 2021;Zhang et al 2021). The work presented here was carried out independently.…”

Galactic gamma-ray and neutrino emission from interacting cosmic-ray nuclei

“…We also used the python packages SciPy (Virtanen et al 2020), NumPy (Harris et al 2020) and Matplotlib (Hunter 2007). We note that in finalising this work, a number of pre-prints related to the results of Amenomori et al (2021) have been made public (Dzhatdoev 2021;Liu & Wang 2021;Qiao et al 2021;Fang & Murase 2021;Koldobskiy et al 2021;Esmaili & Serpico 2021;Nath Maity et al 2022;Zhang et al 2021). The work presented here was carried out independently.…”