Beyond the Standard Model Searches Using a Free Electron Laser

Much of the focus of Beyond the Standard Model physics searches is on the TeV scale, making use of hadron and lepton colliders. Additionally, however, there is the means to make these searches in different regions of parameter space using sub‐electron volt photons from a Free Electron Laser, for example. We report on the experimental results of searches for optical‐wavelength photons mixing with hypothetical hidden‐sector paraphotons in the mass range between 10−5 and 10−2 electron volts for a mixing parameter greater than 10−7. We also report on the results of a sensitive search for scalar coupling of photons to light neutral bosons in the mass range of approximately 1.0 milli‐electron volts and coupling strength greater than 10−6 GeV−1. These were generation‐regeneration experiments using the “light shining through a wall” technique in which regenerated photons are searched for downstream of an optical barrier that separates it from an upstream generation region. The present results indicate no evidence...