Two b or not two b-jets: Measurements of inclusive and dijet b-jet differential cross-sections with the ATLAS detector

This thesis discusses the measurement of the inclusive b-jet cross-section using the 2010 ATLAS dataset and the measurement of di-b-jet cross-sections using the 2011 dataset. The inclusive $b$-jet analysis measured the $p_{\rm T}$ spectrum of $b$-jets in the range 20$<p_{\rm T}<$400 GeV in four rapidity ranges, |y|<0.3, 0.3 < |y| < 0.8, 0.8 < |y| < 1.2 and 1.2 < |y| < 2.1. Good agreement was observed between data and the NLO theory predictions generated by the POWHEG and MC@NLO Monte Carlo generators. However, when the cross-section measurement was split into the |y| regions, MC@NLO showed some shape differences with respect to data. The di-$b$-jet analysis using the 2011 ATLAS dataset measured the di-b-jet cross-section with respect to six different variables. This analysis investigates regions of phase space that are sensitive to different $b\bar{b}$ production mechanisms. It was found that Monte Carlo simulation predicts back- to-back b-jet topologies well. Situations where the b-jets are closer together are more challenging to model and both MC@NLO and POWHEG overpredict the rate of such events.