Book/Dissertation / PhD Thesis

PUBDB-2023-07215

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Differential ratio measurements of $\mathrm{t\bar{t}\gamma}\,/\,\mathrm{t\bar{t}}$ and a search for exclusive $\mathrm{t\bar{t}}$ with the CMS experiment

Ribeiro Lopes, B. (Corresponding author)DESY* ; Jafari, A. (Thesis advisor)Extern*DESY* ; Gallo-Voss, E. (Thesis advisor)DESY*

2023
Verlag Deutsches Elektronen-Synchrotron DESY Hamburg

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Please use a persistent id in citations: doi:10.3204/PUBDB-2023-07215

Report No.: CERN-THESIS-2023-256; DESY-THESIS-2023-019

Abstract: In this thesis, measurements performed using proton-proton collision data at $\sqrt{s} = 13$TeV collected by the CMS experiment at the CERN LHC, in the years 2016, 2017, and 2018, are presented. The data correspond to an integrated luminosity of 138$~\mathrm{fb}^{-1}$.New results on top quark pair production in association with a photon ($\mathrm{t\bar{t}\gamma}$) are presented. Differential cross sections are presented, measuring five different observables that are sensitive to modelling aspects and possible effects of new physics. In particular, top quark observables are measured for the first time, using a top quark pair ($\mathrm{t\bar{t}}$) reconstruction algorithm. Experiment independent distributions are obtained at the parton level.The ratio between the cross sections for $\mathrm{t\bar{t}\gamma}$ and $\mathrm{t\bar{t}}$ is measured for the first time at the LHC, inclusively and differentially. Additionally, the top quark charge asymmetry is measured in $\mathrm{t\bar{t}\gamma}$ events.The results are obtained using maximum likelihood fits which directly account for and constrain backgrounds and systematic uncertainties. The results are compared to theory predictions. No significant deviations from standard model predictions are observed.Using a fraction of the same data, collected in 2017, a search for central exclusive production of $\mathrm{t\bar{t}}$, where the protons remain intact and are measured in the Precision Proton Spectrometer, is also presented. An upper limit for the cross section of this process is obtained.

Note: Dissertation, Universität Hamburg, 2023

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Contributing Institute(s):

1. LHC/CMS Experiment (CMS)

Research Program(s):

1. 611 - Fundamental Particles and Forces (POF4-611) (POF4-611)
2. VH-NG-1302 - Ultimate precision measurements and search for new phenomena in processes with top quarks and a Z boson with the CMS experiment at the LHC (2018_VH-NG-1302) (2018_VH-NG-1302)

Experiment(s):

1. LHC: CMS

Appears in the scientific report 2023

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Database coverage:

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