Abstract
The muon trigger system of the CMS experiment uses a
combination of hardware and software to identify events containing a
muon. During Run 2 (covering 2015–2018) the LHC achieved
instantaneous luminosities as high as 2 × 1034 while
delivering proton-proton collisions at √(s) = 13. The
challenge for the trigger system of the CMS experiment is to reduce
the registered event rate from about 40MHz to about
1kHz. Significant improvements important for the success of
the CMS physics program have been made to the muon trigger system
via improved muon reconstruction and identification algorithms
since the end of Run 1 and throughout the Run 2 data-taking
period. 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. In this paper, the
algorithms used in 2015 and 2016 and their improvements throughout
2017 and 2018 are described. Measurements of the CMS muon trigger
performance for this data-taking period are presented, including
efficiencies, transverse momentum resolution, trigger rates, and the
purity of the selected muon sample. This paper focuses 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.
