5.3.4 Shower-track association

Also of importance for the correct analysis of the data from the calorimeters is the question of shower-track association. Whenever a charged track extrapolates close to a calorimetric shower, the question arises whether the shower is induced by the charged particle, or by a neutral particle that happens to be close-by, or by both the track and a neutral. This effect is simulated by SGV by the routine ZAUCSH. This routine is called by ZAUSHO, if the steering-card MIN_SEP_CLU_TRK is set to a non-zero value. The value of this card is the minimal distance (in cm) between the shower start-point and the track-extrapolation at which the track will be possible to separate from the shower. The routine loops all tracks and all clusters, and compares the two positions, and that way decides if the track will be associated to the cluster, or not. Hence, both mistakes are possible: a track might be associated to a cluster it did not induce, or a track might not be associated to a cluster it d i d induce.