One-loop calculations in quantum field theory: from Feynman diagrams to unitarity cuts

Understand

The success of the experimental program at the Tevatron re-inforced the idea that precision physics at hadron colliders is desirable and, indeed, possible.

• The Tevatron data strongly suggests that one-loop computations in QCD describe hard scattering well.
• Extrapolating this observation to the LHC, we conclude that knowledge of many short-distance processes at next-to-leading order may be required to describe the physics of hard scattering.
• While the field of one-loop computations is quite mature, parton multiplicities in hard LHC events are so high that traditional computational techniques become inefficient.