Data analysis of run0128 (38Ca physics run). The multiplicity distribution of DSSD x-strips is shown in
Attachment 1. The second peak centered at around 128, which is the number of strips of one detector, corresponds
to events where beam-like heavy ions are hitting the detector.
This causes a huge energy deposit in the detector and eventually induces the mirror charge to be shared among
many strips. The number of these events amounts to about 6% of the total (note that only 100000 events were used
for the analysis). A typical charge distribution of such an event is shown in Attachment 2.
We may need to adjust negative thresholds to suppress them. 

EDIT : The same behaviour can be seen on Y strips (see attachment)