Performance of the CMS Level-1 trigger in proton-proton collisions at $$\sqrt{s} =$$ 13 TeV
At the start of Run 2 in 2015, the LHC delivered proton-proton collisions at a center-of-mass energy of 13 TeV. During Run 2 (years 2015-2018) the LHC eventually reached a luminosity of 2.1 × 1034 cm-2 s-1, almost three times that reached during Run 1 (2009-2013) and a factor of two larger than the LHC design value, leading to events with up to a mean of about 50 simultaneous inelastic proton-proton collisions per bunch crossing (pileup). The CMS Level-1 trigger was upgraded prior to 2016 to improve the selection of physics events in the challenging conditions posed by the second run of the LHC. This paper describes the performance of the CMS Level-1 trigger upgrade during the data taking period of 2016-2018. The upgraded trigger implements pattern recognition and boosted decision tree regression techniques for muon reconstruction, includes pileup subtraction for jets and energy sums, and incorporates pileup-dependent isolation requirements for electrons and tau leptons. In addition, the new trigger calculates high-level quantities such as the invariant mass of pairs of reconstructed particles. The upgrade reduces the trigger rate from background processes and improves the trigger efficiency for a wide variety of physics signals.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Los Angeles, CA (United States); Univ. of Colorado, Boulder, CO (United States); Univ. of Florida, Gainesville, FL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF); Kavli Foundation; Nvidia Corporation; SuperMicro Corporation; Welch Foundation; Weston Havens Foundation
- Contributing Organization:
- CMS Collaboration; CMS collaboration
- Grant/Contract Number:
- AC02-07CH11359; C-1845; SC0010005; SC0009937; SC0010266
- OSTI ID:
- 1647071
- Alternate ID(s):
- OSTI ID: 1721773; OSTI ID: 1735494; OSTI ID: 1774594
- Report Number(s):
- FERMILAB-PUB-20-347-CMS; arXiv:2006.10165; CMS-TRG-17-001; CERN-EP-2020-065; oai:inspirehep.net:1801861; TRN: US2202521
- Journal Information:
- Journal of Instrumentation, Vol. 15, Issue 10; ISSN 1748-0221
- Publisher:
- Institute of Physics (IOP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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