Determination of alpha_s via the Differential 2-Jet-Rate with ATLAS at LHC

Lichtnecker, Markus (2011): Determination of alpha_s via the Differential 2-Jet-Rate with ATLAS at LHC. Dissertation, LMU München: Fakultät für Physik

Abstract

The first determination of the strong coupling constant alpha_s via the differential 2-jet-rate in pp collisions at the LHC (at a center-of-mass-energy of 7 TeV) is presented. Data gathered by the ATLAS experiment are fitted by next-to-leading order (NLO) perturbative QCD predictions from calculations with the program NLOJET++. As an observable, the jet-flip-parameter from 3 to 2 reconstructed jets is investigated, using the infrared and collinear safe kT jet algorithm in the exclusive reconstruction mode. The jet-flip-parameters from real data are compared to simulated data from Monte Carlo generators. For the determination of alpha_s, real data have been corrected for the jet-energy-scale, whereas the calculations from NLOJET++ have been corrected for the influence of hadronization effects as well as the impact of the Underlying Event by applying bin-by-bin corrections. The fit between real data and the calculations from NLOJET++ yields a value of alpha_s(M_Z)=0.120 +/-0.001(stat.) +/-0.005(syst.), which is in very good agreement with the current world average.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: ATLAS, alphas, alpha_s, LHC, strong coupling constant
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 530 Physik
• Fakultäten: Fakultät für Physik
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 9. Juni 2011
• 1. Bericht­erstatter:in: Biebel, Otmar