CMS high level trigger performance in run 2

Sert H.

27th Symposium on Nuclear Electronics and Computing, NEC 2019, Budva, Montenegro, 30 September - 04 October 2019, vol.2507, no.7425074, pp.58-64 identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 2507
  • City: Budva
  • Country: Montenegro
  • Page Numbers: pp.58-64
  • Keywords: CMS, HL-LHC, HLT, LHC
  • Istanbul University Affiliated: No


The CMS experiment selects events with a two-level trigger system, the Level-1 (L1) trigger and the High Level trigger (HLT). The HLT is a farm of approximately 30K CPU cores that reduces the rate from 100 kHz to about 1 kHz. The HLT has access to the full detector readout and runs a streamlined version of the offline event reconstruction. In LHC Run 2 the peak instantaneous luminosity reached values around 2×1034 cm−2s−1, posing a challenge to the online event selection. An overview of the object reconstruction and trigger selections used in the 2016-2018 data-taking period will be presented. The performance of the main trigger paths and the lessons learned will be summarised, also in view of the coming LHC Run 3.