Longitudinal Uniformity Scans of PbWO4 Crystals Using 120 GeV Electrons in the H4 Testbeam in 1997

During April and September 1997 data were taken in the H4 testbeam with electrons incident on the side faces ( i.e. perpendicular to the crystal axis) of lead tungstate crystals in order to extract detailed measurements of the longitudinal crystal light collection uniformities. Results are presented for 35 crystals ( five central rows in the 7x7 matrix) with 120 GeV incident electrons. The data were corrected for geometrical effects using a GEANT simulation. The effect of the measured uniformity curves on the ECAL energy resolution was calculated and compared with that predicted from the uniformity curves measured previously at PSI. Both the H4 and PSI data were used to predict the energy resolution constant term and these predictions were compared to the constant term measured directly in H4.