Title Promoter Affiliations Abstract "The CMS experiment at the Large Hadron Collider at CERN." "Pierre Van Mechelen" "Ghent University, Vrije Universiteit Brussel, Particle Physics Group" "To unravel the most fundamental building blocks of matter and how they interact to form the universe around us, is a longterm fascination and challenge of humanity. Participation in the CMS experiment at the LHC particle collider at CERN provides access to the forefront of this international research. With our recent discovery of the Higgs particle, all elementary particles of the Standard Model of particle physics are now observed. We started a unique exploration of how the Higgs particle fits into the model and our experimental verification of the predictability of the model is unprecedented. The omnipresence of dark matter in the universe is only one of the open questions in particle physics for which we seek answers typically by extending the Standard Model with new particles and interactions. Many phenomena related to these extensions can be discovered or tested with our experiment. The scientific ambition of the CMS Collaboration is perfectly aligned with the European Strategy for Particle Physics where the exploration with the LHC and soon its upgraded version is indicated as the highest priority for the field." "The CMS experiment at the CERN Large Hadron Collider" "Jorgen D'Hondt" Physics "Exploring elementary particles and their interactions is an age-old endeavour of humanity. With the 27 km circumference Large Hadron Collider (LHC) at CERN and the monumental detectors around it, scientists from all over the world have access to the most advanced tools to continue this exploration. A major achievement was the experimental confirmation of the existence of the Higgs boson particle in 2012, some 50 years after it had been predicted by Robert Brout, François Englert, and Peter Higgs. Fundamental questions about the reality around us, however, remain, such as, e.g., the nature of dark matter, the matter-antimatter asymmetry, the weakness of gravity, and the unification of all forces. The Compact Muon Solenoid (CMS) detector, to which the Flemish particle physics groups contributed in the design, construction, maintenance, and operation since its conception in the 1990’s, allows to investigate and test many theoretical ideas that are being proposed to answer these questions. This project is vital to pursue this participation so that our groups can collect and analyse “Run 3” data and prepare the CMS detector for the upgraded High-Luminosity LHC" "Differential cross section measurement of top quark-pair production in association with a Z boson in proton-proton collisions at 13.6 TeV with the CMS experiment during LHC Run 3 operation." "Didar Dobur" "Department of Physics and astronomy" "the standard model (SM) is a theoretical model of elementary particles and their fundamental interactions which aims to grasp the phenomena of nature at a fundamental level . However the SM is known to be incomplete as it fails to provide an explanation to several observed phenomena in particle physics. The SM is generally considered to be an effective field theory (EFT), a low‐energy approximation of a more fundamental beyond standard model (BSM) theory. A well‐established framework for probing BSM physics is that of effective field theory interpretation. The impact of EFT operators can be probed with a variety of experimental observables with increased sensitivity to rare top quark process production. The potential to constrain EFT parameters with a differential measurement of top quark‐antiquark pair production in association with a Z boson have been studied in the literature in detail. The inclusion of observables based on reconstructed top quark properties for EFT constrains using a ttZ differential cross section however has not yet been done within the CMS collaboration. This research proposal aims to be a first CMS differential cross section measurement of top quark‐antiquark pair production in association with a Z boson using 13.6 TeV proton-proton collision data at the CMS experiment during LHC Run 3 operation that include top quark reconstructed properties. This will be followed up by a search for new top quark interactions to derive EFT parameter constrains." "New physics in interplay with top quarks: bump hunting in topquark-pair production with two additional quarks at the CMS experiment" "Denise Müller" Physics "With the discovery of the Higgs boson in 2012 at the Large Hadron Collider, the last missing particle as predicted by the standard model (SM) of particle physics was discovered. Nevertheless, there are several open questions for which the SM lacks a suitable explanation. An example is the question as to why the top quark is significantly heavier than all other known elementary particles of the SM. Many theories involving new physics try to explain this heavy mass by a new particle that mostly or even exclusively decays to the top and bottom quark and that has not been discovered yet. Depending on the chosen new physics model, this new particle can reach masses between a few hundreds of GeV and several TeV. Many of these models can be covered simultaneously by a so-called ""bump hunt"" search, a search for a heavy resonance in the invariant mass spectrum of events that contain four top or bottom quarks produced in proton-proton collisions. As these events are highly energetic and their invariant mass spectrum has not been calculated so far, such an analysis is challenging, but yet promising for finding new heavy particles. For this analysis, the Run 3 data that will be recorded by the CMS experiment in the upcoming years is suitable, as around a million top-quark-pair events with two additional quarks are expected to be produced, thus providing sufficient statistics for the search." "The CMS experiment at the Large Hadron Collider at CERN" "Jorgen D'Hondt" "University of Antwerp, Ghent University, Elementary Particle Physics, Physics" "To unravel the most fundamental building blocks of matter and how they interact to form the universe around us, is a longterm fascination and challenge of humanity. Participation in the CMS experiment at the LHC particle collider at CERN provides access to the forefront of this international research. With our recent discovery of the Higgs particle, all elementary particles of the Standard Model of particle physics are now observed. We started a unique exploration of how the Higgs particle fits into the model and our experimental verification of the predictability of the model is unprecedented. The omnipresence of dark matter in the universe is only one of the open questions in particle physics for which we seek answers typically by extending the Standard Model with new particles and interactions. Many phenomena related to these extensions can be discovered or tested with our experiment. The scientific ambition of the CMS Collaboration is perfectly aligned with the European Strategy for Particle Physics where the exploration with the LHC and soon its upgraded version is indicated as the highest priority for the field." "The CMS experiment at the CERN Large Hadron Collider." "Pierre Van Mechelen" "Ghent University, Vrije Universiteit Brussel, Particle Physics Group" "Exploring elementary particles and their interactions is an age-old endeavour of humanity. With the 27 km circumference Large Hadron Collider (LHC) at CERN and the monumental detectors around it, scientists from all over the world have access to the most advanced tools to continue this exploration. A major achievement was the experimental confirmation of the existence of the Higgs boson particle in 2012, some 50 years after it had been predicted by Robert Brout, François Englert, and Peter Higgs. Fundamental questions about the reality around us, however, remain, such as, e.g., the nature of dark matter, the matter-antimatter asymmetry, the weakness of gravity, and the unification of all forces. The Compact Muon Solenoid (CMS) detector, to which the Flemish particle physics groups contributed in the design, construction, maintenance, and operation since its conception in the 1990's, allows to investigate and test many theoretical ideas that are being proposed to answer these questions. This project is vital to pursue this participation so that our groups can collect and analyse ""Run 3"" data and prepare the CMS detector for the upgraded High-Luminosity LHC." "Precision measurements of the top quark and photon interaction with the CMS experiment." "Didar Dobur" "Department of Physics and astronomy" "This project will test standard model prediction by performing precision measurements on top quark pair production (ttbar) with associated photon emission (ttg) using the upcoming CMS data recorded during the third LHC run. The aim is to measure the inclusive and differential cross-sections of ttg, their ratios relative to ttbar cross-sections, and the charge asymmetry in ttg." "Silicon Tracker Endcap for the upgraded CMS experiment at the High-Luminosity LHC at CERN." "Pierre Van Mechelen" "Particle Physics Group" "Scientific curiosity drives us to explore the largest as well as the smallest structures around us. With its 27 km circumference the Large Hadron Collider at CERN collides protons at the highest energies to study the most fundamental building blocks of matter. The recent discovery of the Higgs particle by the ATLAS and CMS experiments was awarded internationally. As a consequence the particle physics community worldwide assigns the top priority to further explore the properties of the Higgs particle as well as to extend our search for new physics phenomena. From 2026 onwards the High-Luminosity LHC will be operational at CERN delivering a 10 times larger dataset of proton collisions to the physicists. This requires the construction of adequate and typically novel detector systems. The Belgian experimental particle physics groups are skilled and motivated to continue their research and leadership in the CMS experiment. The Tracker System is the main system to be innovated and replaced. This Hercules application embraces the construction by the Belgian teams of one Tracker Endcap. This exceptional equipment will be the basis of our research for the next 2 decades." "Measurement of Higgs boson decays to charm quark antiquark pairs in association with top quark antiquark pair production at the CMS experiment." "Didar Dobur" "Department of Physics and astronomy" "The discovery of the Higgs boson at the Large Hadron Collider (LHC) in 2012 completed the standard model (SM) of particle physics. With the addition of the Higgs boson the SM becomes one of the most successful theories to date, as such its predictions agree with the experimental data at the energy scales probed so far remarkably well. On the other hand there exist several observed phenomena in nature, such as dark matter, matter antimatter asymmetry, or the non-zero mass of neutrinos, which hint towards an extended SM. All these constitute a strong motivation to use LHC data to further test the predictions of the SM at an even higher precision. Precise measurement of the properties of the Higgs boson, in particular its interaction strength with elementary particles, is the highest priority of the LHC physics program in the coming years. This proposal focuses on the measurement of the Higgs boson decay to charm quarks in ttH(cc) signatures, where the Higgs boson is produced in association with a top quark antiquark pair. The Higgs boson is predicted to interact with quarks proportional to the particle's mass. With the large amount of data collected by the CMS experiment during LHC Run 2, and what will be collected during Run 3, the measurement of the coupling to lighter quarks like the charm quark will also become accessible. The observation of this coupling will be one of the major milestones expected from the physics program at Run 3." "Deciphering interactions between the top quark and the Higgs boson with the CMS experiment" "Didar Dobur" "Department of Physics and astronomy" "The standard model (SM) of particle physics provides a highly successful description of elementary particles and their interactions. It is nevertheless known to be incomplete but no experimental signs of new physics beyond the SM (BSM) have been found so far. Instead, precision measurements of SM properties become crucial in the search for new physics since small deviations found from SM predictions could hint at BSM physics at a larger energy scale. In this project, the interactions between top quarks (t) and Higgs bosons (H) are to be studied. The top quark, the heaviest known elementary particle, obtains its mass through its Yukawa interaction with the Higgs boson. The study of this coupling is thus essential to understand the mechanism by which particles acquire mass and to search for deviations predicted by many BSM models. The goal of this project is threefold: First, the SM processes of tt̄H, tHq, and tHW production are to be measured with the highest possible precision. Second, flavor-changing neutral currents are to be searched for in top quark-Higgs boson interactions. Third, results of both measurements are to be combined in a global analysis of possible deviations from SM predictions parameterized in the SM effective field theory. The project will use proton-proton collision data recorded by the CMS experiment at the CERN Large Hadron Collider (LHC)."