Production and Detection of Light Dark Matter at Jefferson Lab: The BDX Experiment

The Beam Dump eXperiment (BDX) is a an electron-beam thick-target experiment aimed to investigate the existence of light Dark Matter particles in the MeV-GeV mass region at Jefferson Lab. The experiment will make use of a 10.6 GeV high-intensity electron-beam impinging on the Hall-A beam-dump to produce the Dark Matter particles ($\chi$) through the Dark Photon portal. The BDX detector located at ∼20 m from the dump consists of two main components: an electromagnetic calorimeter to detect the signals produced by the $\chi$-electron scattering and a veto system to reject background. The expected signature of the DM (Dark Matter) interaction in the Ecal (Electromagnetic calorimeter) is a ∼GeV electromagnetic shower paired with a null activity in the surrounding active veto counters. Collecting ${10}^{22}$ electrons on target in 285 days of parasitic run at 65 $\mu$A of beam current, and with an expected background of O(5) counts, in the case of a null discovery, BDX will be able to lower the exclusion limits by one to two orders of magnitude in the parameter space of dark-matter coupling versus mass. This paper describes the experiment and presents a summary of the most significant results achieved thus far, which led to the recent approval of the experiment by JLab-PAC46.