ALP and Z ′ boson at the Electron-Ion Collider

We study the sensitivity of the upcoming Electron-Ion Collider to purely electrophilic new physics in the GeV mass range. Within an effective field theory framework, we consider two different scenarios: an axionlike particle (ALP) and a new heavy neutral vector gauge boson Z ′ ; each couples to electrons only. We analyze electron-proton collisions at s = 141 GeV with an integrated luminosity of 100 fb − 1 , focusing primarily on the trielectron final state. Additionally, loop-induced ALP-photon couplings driven by photon final states are also explored. Incorporating realistic detector effects and systematic uncertainties, we obtain projected exclusion limits on the relevant cross sections and couplings. We find that the results from the Electron-Ion Collider can significantly extend the sensitivity to electrophilic axionlike particles and Z ′ bosons in regions of parameter space that remain weakly constrained by existing experiments.