Testing and Calibration of the Electromagnetic Calorimeter for the Heavy Photon Search Experiment

The Heavy Photon Search (HPS) experiment at Jefferson Laboratory will search for hypothetical massive vector boson, called ``heavy photon.'' The experiment is expected to run in Hall B in the fall of 2014. In this first phase of the measurements, it will search for a heavy photon in the mass range of 20 to 200 MeV/c$^2$. In this mass range the heavy photon will decay into e$^+$e$^-$ pair. An electromagnetic calorimeter (Ecal) will be used to identify electrons and for triggering the readout. The Ecal is made of 442 lead-tungstate (PbWO$^4$) crystals with avalanche photodiode (APD) readout. I will present results from the calibration of cosmic ray testing.