Light dark matter candidates in intense laser pulses I: paraphotons and fermionic minicharged particles

Polarimetric experiments driven by the strong field of a circularly polarized laser wave can become a powerful tool to limit the parameter space of not yet detected hidden-photons and minicharged particles associated with extra U(1) gauge symmetries. We show how the absorption and dispersion of probe electromagnetic waves in the vacuum polarized by such a background are modified due to the coupling between the visible U(1)-gauge sector and these hypothetical degrees of freedom. The results of this analysis reveal that the regime close to the two-photon reaction threshold can be a sensititive probe of these hidden particles. Parameters of modern laser systems are used to estimate the constraints on the corresponding coupling constants in regions where experiments driven by dipole magnets are less constricted. The role played by a paraphoton field is analyzed via a comparison with a model in which the existence of minicharges is assumed only. For both scenarios is found that the most stringent exclusion limit occurs at the lowest threshold mass; this one being determined by a certain combination of the field frequencies and dictated by energy momentum balance of the photo-production of a pair of minicharged particles. The dependencies of the observables on the laser attributes as well as on the unknown particle parameters are also analyzed.