2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/189368A particle $ϕ$ coupling to two photons couples also to charged particles, like protons, through a loop. If the particle is a light scalar this induced coupling to protons leads to non-newtonian forces. We show that the experimental constraints on exotic, fifth-type forces lead to stringent constraints on the $ϕγγ$ coupling.With respect to v1, we have extended the paper, also new authors have joined. Submitted to PRLHigh Energy Physics - Phenomenologytext