Axion and dark photon limits from Crab Nebula high-energy gamma rays

Abstract

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, plus attenuation effects from gamma-ray absorption in the case of dark photon dark matter. Combining the recent $\mathrm{AS}\ensuremath{\gamma}$ and HAWC sub-PeV data with earlier MAGIC and HEGRA data, axionlike particles are most constrained in the $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}--6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\text{ }\text{ }\mathrm{eV}$ mass range, where the coupling ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}$ is constrained to be below $1.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$. Direct scattering from dark photon dark matter limits kinetic mixing $\ensuremath{\epsilon}\ensuremath{\lesssim}{10}^{\ensuremath{-}3}$ for masses between 0.01 and 1 eV.