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Searches for New Physics in Top-Antitop Associated Production Processes and Mechanical Design and Thermal Performance of the CMS Inner Tracker Endcap Pixel Upgrade


Liechti, Sascha. Searches for New Physics in Top-Antitop Associated Production Processes and Mechanical Design and Thermal Performance of the CMS Inner Tracker Endcap Pixel Upgrade. 2024, University of Zurich, Faculty of Science.

Abstract

Three analyses in top-antitop associated production processes are presented. The measurements are based on data collected in proton-proton collisions at √s = 13TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 138 fb−1.

The first measurement is a search for new physics in producing one or more top quarks with additional leptons, jets, and b jets in the context of Effective Field Theory (EFT). EFT effects are incorporated into the event weights of the simulated samples, allowing detector-level predictions that account for correlations and interference effects among EFT operators and between EFT operators and Standard Model (SM) processes. The Wilson Coefficients (WCs) corresponding to 26 EFT operators were simultaneously fit to the data. In all cases, the data is found to be consistent with the SM expectations. Also, a measurement of the Charge-Parity (CP) structure of the Yukawa coupling between the Higgs (H) boson and top quarks at tree level, when the H boson is produced in association with one (tH) or two (t¯tH) top quarks, is presented. The analysis targets events where the H boson decays to leptons and the top quark(s) decay either leptonically or hadronically. CP-even is separated from CP-odd scenarios by applying machine learning techniques to final states characterized by the presence of at least two leptons. No significant CP-odd contribution is observed, and the results are compatible with predictions for the SM H boson.

In addition, the first differential measurement of the production of H bosons in association with either one (tH) or two (t¯tH) top quarks in final states with electrons, muons, and taus are performed. The sensitivity of the analysis is improved by using machine learning methods to separate the signal from the background. The H boson transverse momentum and the mass of the t¯tH system are reconstructed, and differential cross sections for t¯tH production are calculated at the particle level, assuming a lack of new physics effects. The measurement is performed in terms of the H boson pT as well as in terms of the mass of the t¯tH system. Also, a measurement of the H trilinear coupling is performed. At the moment of publishing, this analysis is undergoing the internal review process of the CMS experiment; as such, the plots are marked as ’Work in Progress,’ and the data, numbers, and discussions presented here may differ from the paper’s final version.

Lastly, the TEPX section of the inner tracker of the CMS experiment for the high-luminosity LHC is presented, and studies on the current development of said part are discussed. Several design choices surrounding the mechanical and thermal design were tested and their optimal configuration was selected.

Abstract

Three analyses in top-antitop associated production processes are presented. The measurements are based on data collected in proton-proton collisions at √s = 13TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 138 fb−1.

The first measurement is a search for new physics in producing one or more top quarks with additional leptons, jets, and b jets in the context of Effective Field Theory (EFT). EFT effects are incorporated into the event weights of the simulated samples, allowing detector-level predictions that account for correlations and interference effects among EFT operators and between EFT operators and Standard Model (SM) processes. The Wilson Coefficients (WCs) corresponding to 26 EFT operators were simultaneously fit to the data. In all cases, the data is found to be consistent with the SM expectations. Also, a measurement of the Charge-Parity (CP) structure of the Yukawa coupling between the Higgs (H) boson and top quarks at tree level, when the H boson is produced in association with one (tH) or two (t¯tH) top quarks, is presented. The analysis targets events where the H boson decays to leptons and the top quark(s) decay either leptonically or hadronically. CP-even is separated from CP-odd scenarios by applying machine learning techniques to final states characterized by the presence of at least two leptons. No significant CP-odd contribution is observed, and the results are compatible with predictions for the SM H boson.

In addition, the first differential measurement of the production of H bosons in association with either one (tH) or two (t¯tH) top quarks in final states with electrons, muons, and taus are performed. The sensitivity of the analysis is improved by using machine learning methods to separate the signal from the background. The H boson transverse momentum and the mass of the t¯tH system are reconstructed, and differential cross sections for t¯tH production are calculated at the particle level, assuming a lack of new physics effects. The measurement is performed in terms of the H boson pT as well as in terms of the mass of the t¯tH system. Also, a measurement of the H trilinear coupling is performed. At the moment of publishing, this analysis is undergoing the internal review process of the CMS experiment; as such, the plots are marked as ’Work in Progress,’ and the data, numbers, and discussions presented here may differ from the paper’s final version.

Lastly, the TEPX section of the inner tracker of the CMS experiment for the high-luminosity LHC is presented, and studies on the current development of said part are discussed. Several design choices surrounding the mechanical and thermal design were tested and their optimal configuration was selected.

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Additional indexing

Item Type:Dissertation (monographical)
Referees:Canelli Florencia, Serra Nicola, Isidori Gino
Communities & Collections:07 Faculty of Science > Physics Institute
UZH Dissertations
Dewey Decimal Classification:530 Physics
Language:English
Place of Publication:Zürich
Date:24 April 2024
Deposited On:24 Apr 2024 12:46
Last Modified:21 May 2024 20:49
Number of Pages:151
OA Status:Green
  • Content: Published Version
  • Language: English