HyCal Electromagnetic Calorimeter at Jefferson Lab*

The PrimEx collaboration at Jefferson Lab designed, constructed, and tested a hybrid electromagnetic calorimeter (HyCal) to perform a high precision measurement of the neutral pion lifetime in 2004, using the Primakoff production mechanism on medium and heavy nuclear targets. The initial design requirements for the HyCal calorimeter were high energy and position resolutions together with the large angular acceptance. This was achieved by combining a new high resolution PbWO4 crystal scintillator (inner part) and traditional lead-glass Cherenkov shower detectors (outside part). With its proven high performance and the long-term stability and reliability the HyCal calorimeter was already used in two PrimEx experiments, in one PRad experiment to measure the proton’s charge radius in Hall B at JLab. It will be the main detector for the upcoming planned three experiments: the PRad-II, X17 search, and neutral pion transition form factor measurement experiments in Hall B.

In this talk the design and performance characteristics of this calorimeter will be presented together with the discussion of possible upgrades.