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

We present a study of the expectations for very-high-energy (VHE) to ultra-high-energy (UHE) gamma-ray and neutrino emission from interacting cosmic rays in our Galaxy as well as a comparison to the latest results for the Galactic UHE diffuse emission. We demonstrate the importance of properly accounting for both the mixed cosmic-ray composition and the gamma-ray absorption. We adopt the wounded-nucleon model of nucleus interactions and provide parameterisations of the resulting gamma-ray and neutrino production. Nucleon shielding due to clustering inside nuclei is shown to have a measurable effect on the production of gamma rays and is particularly evident close to breaks and cutoffs in mixed-composition particle spectra. The change in composition around the 'knee' in the cosmic ray spectrum has a noticeable impact on the diffuse neutrino and gamma-ray emission spectra. We show that current and near-future detectors can probe these differences in the key energy range from 10 TeV to 1 PeV, testing the paradigm of the universality of the cosmic ray spectrum and composition throughout the Galaxy.

Automated summary

We present a study on the expected emissions of very-high-energy (VHE) to ultra-high-energy (UHE) gamma-rays and neutrinos from interacting cosmic rays in our Galaxy, and compare them with the latest results for the Galactic UHE diffuse emission. The study highlights the importance of considering both the mixed cosmic-ray composition and gamma-ray absorption. We adopt the wounded-nucleon model for nucleus interactions and provide parameterizations for the resulting gamma-ray and neutrino production. The shielding effect of nucleon clustering inside nuclei is shown to have a measurable impact on gamma-ray production, particularly near breaks and cutoffs in mixed-composition particle spectra. Changes in composition around the cosmic ray spectrum's 'knee' also have noticeable effects on the diffuse neutrino and gamma-ray emission spectra. Current and near-future detectors are capable of probing these differences in the energy range from 10 TeV to 1 PeV, which would help test the paradigm of a universal cosmic ray spectrum and composition throughout the Galaxy.