The silicon-tungsten calorimeters [30] are situated either side of OPAL, 2.389 m in the direction from the interaction point. They were installed in 1993 to give an improvement on the luminosity measurement. They are sampling calorimeters and consist of 19 layers of sampling silicon separated by 18 layers of tungsten. Each calorimeter is divided azimuthally into 16 wedges and can achieve a spatial resolution in of 10 m and an energy resolution in units of GeV of:
(2.5) |