PPP Theory Seminar: Jiayin Gu (Johannes Gutenberg University of Mainz), "Amplitudes, sum rules and positivity bounds in the SMEFT"

Tuesday 23 Mar 2021, 10:00 → 11:00 US/Central

Meeting link: https://kansas.zoom.us/j/92638240546

Meeting ID: 926 3824 0546

Passcode: 779046

Abstract: The dispersion relation of an elastic 4-point amplitude in the forward direction leads to a sum rule that connects the low energy amplitude to the high energy observables.  We discuss the implication of these sum rules on the dimension-6 operators in the SMEFT, and point out their interesting connections with the custodial symmetry of the SM Higgs and fermion sectors.  These dispersion relations also lead to positivity bounds on certain dimension-8 operator coefficients.  While these dimension-8 operators are generally difficult to probe, we point out a special channel, e+e-  ->  gamma gamma, for which the leading contribution comes from dimension-8 operators, and the corresponding positivity bounds can be directly probed.   We also demonstrate the usefulness of the helicity amplitude formalism in both cases. 

Based on arXiv:2008.07551 and 2011.03055.

sumpos6.pdf

zoom_0.mp4