New Results from a Search for Dark Photons with the FASER Detector at the LHC

FASER is an experiment at the LHC designed to search for light, feebly-interacting particles produced in proton-proton collisions at the ATLAS interaction point that travel in the far forward direction. Here we present results from a search for dark photons decaying to electron-positron pairs using a dataset corresponding to an integrated luminosity of 177~$\text{fb}^{-1}$. This dataset was collected at a center-of-mass energy $\sqrt{s} = 13.6$~TeV in 2022, 2023, and 2024 during LHC Run 3. No events are seen in a nearly background-free analysis, resulting in world-leading constraints on dark photons with couplings $\epsilon \sim 10^{-5} - 10^{-4}$ and masses $\sim10~\text{MeV} - 150$~MeV.