Doctoral Dissertation Open Access

Jet energy calibration and triple differential inclusive cross section measurements with Z (→μμ) + jet events at 13 TeV recorded by the CMS detector

Berger, Thomas

Thesis supervisor(s)

Quast, Günter; Rabbertz, Klaus

This thesis presents two substantial aspects of the analysis of Z boson production in association with jets, where the Z boson decays to a muon-antimuon pair: jet energy calibration and triple differential cross section measurements.
Data have been used that were recorded with the CMS detector in the year 2016 at a center-of-mass energy of 13 TeV. These data correspond to an integrated luminosity of 35.9 fb-1 of proton-proton collisions at the LHC. The first part of this thesis contributes to the jet energy calibration in CMS by estimating residual corrections that account for differences in jet reconstruction between measurement and simulation. Correction factors are extracted from Z (→ μμ) + jet events by comparing the transverse momentum of a jet to the one of a balancing Z boson, which can be reconstructed very precisely from muons.
The second part of this thesis presents triple differential measurements of inclusive cross sections for Z (→ μμ) + jet production. The cross sections are measured as a function of the Z boson transverse momentum pTZ or alternatively  the variable ϕ*η, the rapidity separation y* of the Z boson and the leading jet, and the boost yb of their center-of-mass system. The observable ϕ*η has the advantage to be determined from angular information of the muons only, thereby further increasing the reconstruction precision in comparison to pTZ. The observables y* and yb introduce a division of the phase space that promises a better sensitivity to the parton subprocesses and thus the PDFs. The measured cross sections are corrected for detector effects by a three-dimensional unfolding procedure and are compared to theory predictions calculated at next-to-next-to-leading order in perturbative QCD.

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