New methods for computing QCD loop amplitudes for the LHC

by Lance Dixon (SLAC)

Tuesday 28 Oct 2008, 16:45 → 18:15 Europe/Berlin

Hoersaal (MPI)

Over the next decade, the search for the Higgs boson and for new physics at short distances will be carried out by colliding protons at the Large Hadron Collider at CERN. These searches have significant backgrounds from "old physics" -- the production of Standard Model particles, often including many jets from emission of quarks and gluons. Better theoretical predictions for these backgrounds can be obtained by working at next-to-leading order in the strong coupling. A major bottleneck in doing so comes from the difficulty in computing one-loop scattering amplitudes for many external particles. Thousands of complicated Feynman diagrams have to be summed. Yet the sum of all diagrams is often much simpler than the typical diagram, suggesting hidden symmetries and better ways to compute. Over the past few years, spinoffs from "twistor string theory", related to the general analytic properties of scattering amplitudes, have led to efficient alternatives to Feynman diagrams, which promise to help improve our ability to find new physics at the LHC.