# Measurement of the inclusive and differential $t$-channel single top quark production cross section at 13 TeV with the CMS experiment

Seith, David

##### Abstract:
A measurement of the inclusive and differential $t$-channel single top quark production cross section is performed in this thesis.
The measurement uses 137 fb$^{-1}$ of data recorded at the CMS experiment at the LHC with a center-of-mass energy of 13 TeV.
Events are selected with exactly one muon or electron and two or three jets, of which at least one is identified as originating from a bottom quark.
In the analysis an improved technique for reconstructing the top quark has been developed that makes use of a neural network in order to achieve a better description of the top quark's kinematic variables.
A multiclassification BDT is used to classify events into different process categories.

The cross sections are extracted from a fit to the output distribution of the multiclassification BDT.
The inclusive cross section of $t$-channel single top quark production was measured to be $\sigma_{\mathrm{t}} = 130 \pm 20 \, \mathrm{pb}$ and the cross section of top antiquark production to be $\sigma_{\mathrm{\bar{t}}} = 80 \pm 15 \, \mathrm{pb}$.

The differential cross section measurement is performed via unfolding.
The measured differential cross sections as a function of the top quark transverse momentum and rapidity agree with the predictions of the SM.
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 Zugehörige Institution(en) am KIT Institut für Experimentelle Teilchenphysik (ETP) Publikationstyp Hochschulschrift Publikationsdatum 01.03.2021 Sprache Englisch Identifikator KITopen-ID: 1000128926 Verlag Karlsruher Institut für Technologie (KIT) Umfang xii, 172, xxvi S. Art der Arbeit Dissertation Fakultät Fakultät für Physik (PHYSIK) Institut Institut für Experimentelle Teilchenphysik (ETP) Prüfungsdatum 18.12.2020 Referent/Betreuer Prof. T. Müller Schlagwörter single top, top quark, LHC, CMS, 13 TeV, cros section, polarization, Run 2
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