Self-consistent model with vector and scalar mediators and prospects for light dark matter searches in e+e−-collisions

In this work, we consider a theoretically motivated self-consistent model of light dark matter interacting with the standard model fields via vector and scalar portals. The model features an additional [Formula: see text] gauge symmetry, a vector boson kinetically mixed with the standard model hypercharge field, and a scalar singlet coupled to the Higgs sector via mixing. We present exact forms of the interaction Lagrangians and focus on the parameter space characterized by small mixing and light mediators. A numerical simulation is performed for the process of associated dark matter production with a [Formula: see text] pair in [Formula: see text] collisions at [Formula: see text]. Signal and background cross sections are calculated, and expected sensitivity contours are presented in the parameter space [Formula: see text]. We find that even with small values of the scalar mixing parameter, [Formula: see text], the scalar-mediated contribution remains phenomenologically significant within the self-consistent framework, especially compared to models with only a vector mediator.