Novel Unfolding Methods and Measurements of tt ̄ Differential Cross Sections with SMEFT interpretation using the ATLAS detector at the LHC

Studies on unfolding methods and measurements of tt ̄ differential cross sections in
the l+jets decay channel at the Large Hadron Collider are presented in this thesis.
Available and novel unfolding algorithms are compared using known and new figures
of merit and a response matrix estimation method that is less dependent on the
size of the training data. Lastly, a novel covariance matrix estimation method is
presented that includes both statistical and systematic uncertainties from various
sources. Measurements of tt ̄ production cross sections in the l+jets decay channel
at the Large Hadron Collider are presented. A total integrated luminosity of 139
fb−1 of proton-proton collision data at a centre-of-mass energy of √s = 13 TeV has
been collected at the ATLAS detector. The production cross section as a function
of several kinematic variables are measured, unfolded and compared to theory. The
unfolded differential cross sections are used to estimate and constrain the c8 and c8,1 tq Qq Wilson coefficients of the Standard Model Effective Field Theory with individual and two-parameter fits using LO and NLO QCD SMEFT predictions. The results are found to be in good agreement with the SM.