21 research outputs found

    Development of a DAQ system for the CMS ECAL Phase 2 recommissioning

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    In view of the High-Luminosity phase of the Large Hadron Collider (LHC), in the barrel region of the CMS electromagnetic calorimeter (ECAL) the entire readout electronics will be replaced to cope with the more stringent requirements in terms of trigger latency, acquisition rate, and radiation and pileup resilience. The configuration sequence for the new on-detector electronics, involving both the improved very-front-end and front-end cards, is reported. The sequence of commands and parameters to load in the electronics is controlled by a software developed at CERN by the ECAL upgrade group and it will be the base on which to build the new data acquisition system (DAQ)

    Design of the CMS High Granularity Calorimeter trigger primitive generator system

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    The CMS collaboration has chosen a novel high granularity calorimeter (HGCAL) to instrument the endcap regions as part of its upgrade for the high luminosity LHC. The HGCAL will have fine segmentation in both the transverse and longitudinal directions and will be the first such calorimeter specifically optimised for particle flow reconstruction to operate at a colliding-beam experiment. The calorimeter data will be part of the Level 1 trigger of the CMS experiment and, together with tracking information, will allow particle-flow techniques to be used in this first level trigger. The Level 1 trigger has tight constraints on latency and rate and will be implemented in hardware. The high granularity leads to about six million readout channels in total, that are concentrated in one million trigger cells, sampled at 40 MHz for the Level 1 trigger. This presents a significant challenge in terms of data manipulation and data processing for the trigger system as the trigger data volumes will be an order of magnitude above those currently handled in CMS. In addition, the high luminosity will result in an average of up to 200 interactions per bunch crossing that yield a huge background rate in the forward region that will need to be efficiently rejected by the trigger algorithms. Furthermore, reconstruction of the three-dimensional particle clusters to be used for particle flow in events with high hit rates is also a complex computational problem for the trigger. The status of the HGCAL trigger architecture and design, as well as the various challenges encountered and the methodologies developed to improve these major aspects, will be presented

    A sensitivity study of VBS and diboson WW to dimension-6 EFT operators at the LHC

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    We present a parton-level study of electro-weak production of vector-boson pairs at the Large Hadron Collider, establishing the sensitivity to a set of dimension-six operators in the Standard Model Effective Field Theory (SMEFT). Different final states are statistically combined, and we discuss how the orthogonality and interdependence of different analyses must be considered to obtain the most stringent constraints. The main novelties of our study are the inclusion of SMEFT effects in non-resonant diagrams and in irreducible QCD backgrounds, and an exhaustive template analysis of optimal observables for each operator and process considered. We also assess for the first time the sensitivity of vector-boson-scattering searches in semileptonic final states.Comment: Final version after editor's revision. Improved text descriptions and plots styling. Added subparagraph in chapter 5.1 discussing the impact of SMEFT corrections in propagators which was previously ignore

    Search for long-lived heavy neutral leptons with lepton flavour conserving or violating decays to a jet and a charged lepton

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    International audienceA search for long-lived heavy neutral leptons (HNLs) is presented, which considers the hadronic final state and coupling scenarios involving all three lepton generations in the 2-20 GeV HNL mass range for the first time. Events comprising two leptons (electrons or muons) and jets are analyzed in a data sample of proton-proton collisions, recorded with the CMS experiment at the CERN LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb‚ąí1^{-1}. A novel jet tagger, based on a deep neural network, has been developed to identify jets from an HNL decay using various features of the jet and its constituent particles. The network output can be used as a powerful discriminating tool to probe a broad range of HNL lifetimes and masses. Contributions from background processes are determined from data. No excess of events in data over the expected background is observed. Upper limits on the HNL production cross section are derived as functions of the HNL mass and the three coupling strengths V‚ĄďNV_{\ell\mathrm{N}} to each lepton generation ‚Ąď\ell and presented as exclusion limits in the coupling-mass plane, as lower limits on the HNL lifetime, and on the HNL mass. In this search, the most stringent limit on the coupling strength is obtained for pure muon coupling scenarios; values of ‚ą£VőľN‚ą£2>\lvert V_{\mu\mathrm{N}}\rvert^{2}\gt 5 (4)√ó\times10‚ąí7^{-7} are excluded for Dirac (Majorana) HNLs with a mass of 10 GeV at a confidence level of 95% that correspond to proper decay lengths of 17 (10) mm

    Elliptic anisotropy measurement of the f0_0(980) hadron in proton-lead collisions and evidence for its quark-antiquark composition