Measuring the Acceleration-Dependent Temperature of the Minkowski Vacuum

Relativistic quantum field theory is the structure on which the Standard Model and beyond-Standard Model physics are built. One of its most striking predictions is the Unruh effect: an accelerating observer measures the Minkowski vacuum as a thermal bath at a fixed temperature. Despite decades of theoretical interest, this effect has never been directly observed. We propose to use the high acceleration gradients provided by wakefield accelerators, coupled with a forward laboratory-frequency ~THz detector array, to measure the resulting forward-beamed radiation, and outline the unique signature provided by quantum detailed balance to extract the signal from backgrounds. While challenging, such a measurement appears within reach of present-day accelerator and detector technologies.