This thesis presents results for the determination of the QCD jet energy scale and the single top quark cross-section. Hadron jets are the most commonly observed objects in p-p collisions at the Large Hadron Collider at CERN. Because of this, they are part of the final state of almost any process, and are an important part of all searches for extensions of the Standard Model. This thesis presents an in situ determination of the jet energy scale with a systematic uncertainty of less than 3\%. Single top quark production at the LHC is a sensitive probe of physics beyond the standard model, and is itself an important background for Higgs searches. In this thesis, data-driven models for important backgrounds to single top quark events are developed, and are used to measure the t-channel single top quark production rate in 35 / picobarns of integrated luminosity.