Testing large non-standard neutrino interactions with arbitrary mediator mass after COHERENT data

In the presence of neutrino Non-Standard Interactions (NSI) with matter, the derivation of neutrino parameters from oscillation data must be reconsidered. In particular, along with the standard solution to neutrino oscillation, another solution known as LMA-Dark is compatible with global oscillation data and requires both 0(12) > pi/4 and a certain flavor pattern of NSI with an effective coupling comparable to G(F). Contrary to conventional expectations, there is a class of models based on a new U(1)(X) gauge symmetry with a gauge boson of mass of few MeV to few 10MeV that can viably give rise to such large NSI. These models can in principle be tested by Coherent Elastic nu-Nucleus Scattering (CE nu NS) experiments such as COHERENT and the upcoming reactor neutrino experiment, CONUS. We analyze how the recent results from the COHERENT experiment constrain these models and forecast the discovery potential with future measurements from COHERENT and CONUS. We also derive the constraints from COHERENT on lepton flavor violating NSI.