Dark force detection in low energy e- p collisions

We study the prospects for detecting a light boson X with mass m _X ≾ 100 MeV at a low energy electron-proton collider. We focus on the case where X dominantly decays to e ⁺ e ^- as motivated by recent “dark force” models. In order to evade direct and indirect constraints, X must have small couplings to the standard model (α _X ≾ 10^-8) and a sufficiently large mass ( m _X ≳ 10 MeV). By comparing the signal and background cross sections for the e ^- p e ⁺ e ^- final state, we conclude that dark force detection requires an integrated luminosity of around 1 ab^-1, achievable with a forthcoming JLab proposal.