Abstract
The trigger systems of the LHC detectors play a crucial role in determining the physics capabilities of the experiments. A reduction of several orders of magnitude of the event rate is needed to reach values compatible with the detector readout, offline storage and analysis capabilities. The CMS experiment has been designed with a two-level trigger system the Level 1 (L1) Trigger, implemented on custom-designed electronics, and the High Level Trigger (HLT), a streamlined version of the CMS reconstruction and analysis software running on a computer farm. Here we will present the design and performance of the main muon, electron and photon triggers, in view of the more challenging conditions for the LHC Run 2. For the muon case, we discuss the improvements in the isolation algorithm with the usage of Particle Flow techniques, which allow for better discrimination power between processes with prompt muons and the the effect of jets penetrating through the hadronic calorimeter into the muon chambers. For the electron and photon cases, we discuss the identification variables used to distinguish between prompt electrons/photons and hadronic jets enriched in electromagnetic component. Presented at LP2015 XXVII International Symposium on Lepton Photon Interactions at High Energies Performance of electron, photon and muon triggers at the CMS High Level Trigger Thiago R. F. P. Tomei∗ On behalf of the CMS Collaboration Instituto de Fisica Teorica, Universidade Estadual Paulista E-mail: Thiago.Tomei@cern.ch The trigger systems of the LHC detectors play a crucial role in determining the physics capabilities of the experiments. A reduction of several orders of magnitude of the event rate is needed to reach values compatible with the detector readout, offline storage and analysis capabilities. The CMS experiment has been designed with a two-level trigger system: the Level 1 (L1) Trigger, implemented on custom-designed electronics, and the High Level Trigger (HLT), a streamlined version of the CMS reconstruction and analysis software running on a computer farm. Here we will present the design and performance of the main muon, electron and photon triggers, in view of the more challenging conditions for the LHC Run 2. For the muon case, we discuss the improvements in the isolation algorithm with the usage of Particle Flow techniques, which allow for better discrimination power between processes with prompt muons and the the effect of jets penetrating through the hadronic calorimeter into the muon chambers. For the electron and photon cases, we discuss the identification variables used to distinguish between prompt electrons/photons and hadronic jets enriched in electromagnetic component. International Symposium on Lepton Photon Interactions at High Energies 17-22 August 2015 University of Ljubljana, Slovenia ∗Speaker. c © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). http://pos.sissa.it/ Performance of electron, photon and muon triggers at the CMS HLT Thiago R. F. P. Tomei
Highlights
With the beginning of the LHC Run 2, the CMS experiment has to cope with harsher operating conditions: higher centre-of-mass energy of 13 TeV, leading to an enhancement of the production cross section of interesting processes like weak boson and top quark production, and larger occurrence of multiple proton-proton interactions in the same / near bunch crossings, ranging from 20 to 40 simultaneous interactions
A new approach to isolation has been developed for Run 2, based on Particle Flow clusters and sequential isolation
The identification of electrons and photons at CMS relies on the granularity of ECAL and on the high performance of the tracker, both during off-line reconstruction and at the High Level Trigger (HLT)
Summary
With the beginning of the LHC Run 2, the CMS experiment has to cope with harsher operating conditions: higher centre-of-mass energy of 13 TeV, leading to an enhancement of the production cross section of interesting processes like weak boson and top quark production, and larger occurrence of multiple proton-proton interactions in the same / near bunch crossings (pileup), ranging from 20 to 40 simultaneous interactions. The High-Level Trigger software [1] has been optimised for these conditions, balancing a high selection efficiency on signal events while keeping the output rate at acceptable levels both for the online data acquisition system and the offline prompt reconstruction center. In this paper we discuss the improvements made for e, γ and μ trigger algorithms
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
