Track Competition for Clone and Ghost Removal

At the beginning of this phase of the reconstruction all track candidates are sorted according to their length. Starting with the longest candidate the algorithm marks all hits belonging to these candidates as used. Proceeding track by track, the algorithm checks how many hits belonging to the track have already been used. If the fraction of used hits exceeds some predefined level (in the current version -- 30%), the track is discarded. If the track has survived, all its hits are marked as used.

Figure 4.6: The final event reconstruction.

The main idea of this procedure is straightforward: to favor the longest tracks and to get rid of short ghost tracks and nearby clones^4.1. Studies on simulated data have shown that this track competition procedure drastically reduces the ghost level while the reconstruction efficiency is only slightly reduced. The event already depicted in Fig. 4.5 is again shown in Fig. 4.6 after clones and ghosts are removed.