Vertex finding performance studies for the Phase II CMS Level-1 Trigger

At the HL-LHC, a significant increase in the luminosity delivered to CMS will result in a pileup per bunch crossing of 140-200. This provides a difficult environment to obtain reliable physics results and keep trigger rates manageable. In order to mitigate this problem, tracker information will be used, for the first time, at the Level-1 (L1) trigger. This will allow the primary vertex reconstruction at L1. In this report, an investigation into the vertex finding performance of a potential algorithm is presented. The vertex finding efficiency was measured as a function of several variables, such as the percentage of tracks associated to the primary vertex within the barrel and the pT of the tracks. The efficiency was found to not depend significantly on the pileup for the samples analyzed, however, a strong dependence was observed on the number of tracks associated with the primary vertex.