Ultrahigh energy photons striking matter can transform into rho mesons through an interaction that involves many nuclei simultaneously, a phenomenon that may affect the detection signatures of high-energy particles from space. When an energetic photon smashes into matter, it can create a massive particle, the rho meson, when it strikes an atomic nucleus. A report in the 7 August Physical Review Letters shows that such a photon can also produce the particle in an interaction that involves many nuclei simultaneously. This so-called coherent production grows in importance as the photon energy increases and must be accounted for in analyses of data from the highest energy particles from space, including cosmic rays and neutrinos.
