The observation of cosmic sub-PeV gamma-rays from the Crab Nebula opens up the possibility of testing cosmic ray photon transparency at the multi-hundred TeV scale. Assuming no deviation from a source gamma-ray emission due to accelerated electron inverse-Compton scattering, higher event energies can extend constraints on the effects of new physics; We consider oscillation between gamma-rays and axions/dark photons, plus attenuation effects from gamma-ray absorption in the case of dark photon dark matter. Combining the recent AS$\gamma$ and HAWC sub-PeV data with earlier MAGIC and HEGRA data, axion-like particles are most constrained in the $10^{ -7}-10^{ -6}$ eV mass range, where the coupling $g_{ a\gamma}$ is constrained to be below ${ 1.8}\times 10^{ -10}$ GeV$^{ -1}$. In comparison, gamma ray flux attenuation due to oscillation with a dark photon leads to a very weak constraint on the mixing parameter; $\epsilon\lesssim$ 0.2 for dark photon mass between $10^{ -7}$ and $10^{ -6}$ eV. Direct scattering from dark photon dark matter limits $\epsilon\lesssim$ 0.01 for masses between $6$ and $400$ eV.
Categories: astro-ph.HE hep-ph