to the Fermilab accelerator complex. In addition, both the CDF [11] and DØ detectors [12] were upgraded. The results reported here utilize an order of magnitude higher integrated luminosity than reported previously [5]. The theory of QCD describes the behavior of those particles (quarks q and gluons g ) that experience the strong force. It is broadly modeled on the theory of Quantum Electrodynam- ics (QED), which describes the interactions between electrically-charged particles. However, unlike the electrically-neutral photon of QED, the gluons, the force-mediating bosons of the strong interaction, carry the strong charge. This fact greatly increases the complexity in calculating the behavior of matter undergoing interactions via the strong force. The mathematical techniques required to make these calculations can be found in text- books (e.g. [13]). Instead of giving an exhaustive description of those techniques here, we focus on those aspects of the calculations employed most frequently in the experimental analysis, thereby clarifying the phenomena experimentalists investigate. II. PERTURBATIVE QCD FIG. 1: Stylized hadron-hadron collision, with relevant features labeled. Note that a LO calculation of the hard scatter (dashed line) will assign a jet to final state radiation that would be included in the hard scatter calculation by a NLO calculation (dotted line). 3