Constraining Disformally Coupled Scalar Fields

Light scalar fields can naturally couple disformally to matter fields. Static, non-relativistic sources do not generate a classical field profile for a disformally coupled scalar, and so such scalars are free from the constraints on the existence of fifth forces that are so restrictive for conformally coupled scalars. In this work we show that disformally coupled scalars can still be studied and constrained through their microscopic interactions with fermions and photons, both in terrestrial laboratories and from observations of stars. The strongest constraint on the coupling scale comes from mono-photon searches at the LHC and requires $M \gtrsim 10^2 \mbox{ GeV}$.