| Thesis | |
| Report number | CERN-THESIS-2011-369 |
| Title | Determination of $\alpha_{s}$ via the Differential 2-Jet-Rate with ATLAS at LHC |
| Author(s) | Lichtnecker, Markus (Munich U.) |
| Publication | 122. |
| Thesis note | PhD : Munich U. : 2011 |
| Thesis supervisor(s) | Biebel, Otmar |
| Subject category | Particle Physics - Experiment |
| Accelerator/Facility, Experiment | CERN LHC ; ATLAS |
| 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. |
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