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.