Pinpointing the knee of cosmic rays with diffuse PeV gamma-rays and neutrinos

Understand

The origin of the knee in cosmic ray spectrum remains to be an unsolved fundamental problem.

• There are various kinds of models which predict different break positions and the compositions of the knee.
• In this work, we suggest to use diffuse $\gamma$-rays and neutrinos as probes to test these models.
• Based on several typical types of the composition models, the diffuse $\gamma$-ray and neutrino spectra are calculated, which show distinctive cutoff behaviours at energies from tens of TeV to multi-PeV.