Test beam analysis of the effect of highly ionizing particles on the CMS Silicon Strip Tracker

Highly ionizing particles (HIPs) created by nuclear interactions in the silicon sensors cause a large signal which can saturate the APV readout chip used in the CMS Silicon Tracker system. This phenomenon was studied in two different beam-tests performed at PSI and at the CERN X5 experimental areas in 2002. The probability of a HIP-like event to occur per incident pion was measured and the dependence of the APV capability to detect a MIP signal on the time required to recover from such an event is derived. From these results, the expected inefficiency of the CMS Tracker due to HIPS is inferred.