Measurement of Top-Quark Mass and Inclusive Top-Quark-Pair Production Cross Section in pp Collisions at $\sqrt{s} = 7/8$ TeV with CMS

One of the most intriguing particles in the Standard Model is the top quark, theheaviest fundamental particle known to date. In this thesis, the mass of the top quarkand the production cross section for top-quark pairs are measured from events with atop-quark pair decaying only into hadrons. This challenging decay mode features a highrate but is drowned by multijet background events. The top quarks are produced at theLarge Hadron Collider and the decay products are detected with the Compact MuonSolenoid experiment. Data collected at centre-of-mass energies of 7 and 8 TeV withintegrated luminosities of 3.54 fb−1 and 18.2 fb−1 is used for the presented measurements.In order to improve the reconstruction and identification of the desired events,constrained least-squares fitting is utilised, which exploits the kinematics of top-quarkpair events. The top-quark mass and the production cross section for top-quark pairs areextracted using likelihoods from events with at least six jets created from the hadronsin the final state. In order to reduce systematic uncertainties on the result, their mainsources are incorporated into the likelihoods and are estimated in parallel with the massitself. Combining all these methods, the most precise measurement of the top-quarkmass from all-jets events so far is achieved. The top-quark mass is measured to be172.08 ± 0.90 GeV.