"Unitary Cuts and Loop Amplitudes in QCD and Supersymmetric Theories" by Mao Zeng (UCLA Physics & Astronomy)

Tuesday, October 3, 2017 - 4:00pm to 5:00pm
TEP Seminar

Abstract: In the study of multi-loop scattering amplitudes, the method of generalized unitarity cuts has been very successful in the construction of loop integrands. Very recently, progress has also been made on the front of loop integration. We present the first calculation of a 2-loop QCD amplitude relevant for LHC physics using numerical unitarity, by deriving integration-by-parts relations from the geometry of unitarity cut surfaces. As another application, we calculate the "leading transcendental" part of the 5-loop UV divergence of N=8 supergravity, in an effort to test various proposals about the UV behavior of the theory. Surprisingly, dual conformal symmetry, most studied as a hidden symmetry of N=4 SYM, gives additional insights into loop integrals even in QCD, because the geometry of the unitarity cut surface is not sensitive to the matter content. As a side product, we find hints of an analog of dual conformal symmetry in the nonplanar sector of N=4 SYM.

PAB 4-330