Toward the Detection of Relativistic Image Doubling in Imaging Atmospheric Cerenkov Telescopes
Cosmic gamma-ray photons incident on the upper atmosphere may create air showers that move to the Earth's surface with superluminal speed, relative to the air. Although these air showers likely remain superluminal all along their trajectories, the velocity component toward a single Imaging Atmospheric Cherenkov Telescope (IACT) may drop from superluminal to subluminal. When this happens, an IACT that is able to resolve the air shower both in time and angle should be able to document an unusual effect known as relativistic image doubling (RID). The logic of RID is that the shower appears to precede its own Cherenkov radiation when its speed component toward the IACT is superluminal, but appears to trail its own Cherenkov radiation when its speed component toward the IACT is subluminal. The result is that the IACT will see the shower start not at the top of the atmosphere but at the point along the shower's path where its speed component toward the IACT drops from superluminal to subluminal, after which the shower will appear to this IACT to go both up and down simultaneously. Simulations that demonstrate this effect conceptually are presented. To date, no RID effect has yet been reported outside the lab. It is speculated that identifying RID effects in the Earth's atmosphere is not only interesting in its own right, but may allow a more accurate reconstruction of the path and speed profile of photon-triggered, Cherenkov-generating, atmospheric air showers.