Performance of the CMS muon trigger system in proton-proton collisions at 13 TeV

During Run 2 (covering 2015–2018) the LHC achieved a maximum instantaneous luminosity of 2 × 1034cm−2s−1 while delivering proton-proton collisions at √ B = 13 TeV. The challenge for the trigger system of the CMS experiment is to reduce the event rate from about 40 MHz to about 1 kHz. In this document, muon reconstruction and identification algorithms used during Run 2 and their improvements are presented. The new algorithms maintain the acceptance of the muon triggers at the same or even lower rate throughout the data-taking period despite the increasing number of additional proton-proton interactions in each LHC bunch crossing. We will focus on the single and double muon triggers with the lowest sustainable transverse momentum thresholds used by CMS. The efficiency is measured in a transverse momentum range from 8 to several hundred GeV.