Searching for Axions from Atmospheric Kaon Decays

Cosmic-ray interactions in the Earth’s atmosphere produce copious secondary mesons, providing a natural laboratory for searches for new physics. We investigate the atmospheric production of axions through the rare kaon decay $K^{+}\to {\pi }^{+}a$. If sufficiently long-lived, these axions can reach large underground detectors such as Super-Kamiokande and IceCube and decay through the diphoton channel, $a\to \gamma \gamma$. Using data from Super-Kamiokande and IceCube, we derive constraints on the axion decay constant $f_a$ for masses up to $m_a\sim 350\mathrm{M}\mathrm{e}\mathrm{V}$. We demonstrate that atmospheric kaon decays provide a novel probe of axion parameter space, yielding constraints complementary to existing bounds.