In short, the calibration goes in two steps. At first, in the course of data analysis, the data on single track electron events are collected by means of the signal of Gas Cherenkov counter. Then, by the end of replay, a calibration is done on the collected data.
(For questions and comments contact Vardan Tadevosyan, tadevosn@jlab.org or Hamlet Mkrtchyan, hamlet@jlab.org)