Searching for Visibly Decaying Displaced Dark Photons with the Heavy Photon Search Experiment

A popular model for light (sub-GeV) Dark Matter is that its constituents belong to a Hidden Sector, uncharged under the Standard Model (SM) forces, and coupled to the SM through a new force carrier. In particular, theoretically well-motivated models propose the existence of a new U(1) light gauge boson, called the heavy (or dark) photon A' which kinetically mixes with the SM photon. The Heavy Photon Search (HPS) at the Thomas Jefferson National Accelerator Facility (JLAB, USA) has been primarily designed to search for electro-produced heavy photons decaying into electron-positron pairs. HPS is sensitive to an experimental signature where the heavy photon decays with displayed vertices. In this presentation, I will describe the design and performance of the HPS detector before outlining the results of the displaced vertex analysis of data collected during the 2016 engineering run. Moreover, I will talk about the status of the ongoing analysis of two additional, larger datasets from 2019 and 2021 and present a reach estimate for these new data.