The Heavy Photon Search beamline and its performance

Understand

The Heavy Photon Search (HPS) is an experiment to search for a hidden sector photon, aka a heavy photon or dark photon, in fixed target electroproduction at the Thomas Jefferson National Accelerator Facility (JLab).

• The HPS experiment searches for the e$^+$e$^-$ decay of the heavy photon with bump hunt and detached vertex strategies using a compact, large acceptance forward spectrometer, consisting of a silicon microstrip detector (SVT) for tracking and vertexing, and a PbWO$_4$ electromagnetic calorimeter for energy measurement and fast triggering.
• To achieve large acceptance and good vertexing resolution, the first layer of silicon detectors is placed just 10 cm downstream of the target with the sensor edges only 500 $\mu$m above and below the beam.
• Placing the SVT in such close proximity to the beam puts stringent requirements on the beam profile and beam position stability.