Speaker: R. Sekhar Chivukula
Title:Scattering Amplitudes and Sum Rules for Massive Spin-2 States
Host: Da Liu
Zoom: https://zoom.us/j/186024391
Abstract:
Spin-2 Kaluza-Klein states arise in many theoretical contexts, from string theory and AdS/CFT to phenomenological models of particle physics and dark matter; they are also the focus of experimental searches at the LHC. A key question that influences their phenomenology and the range of validity of any effective field theories built around them is how quickly scattering amplitudes involving these modes grow with energy. The faster they grow, the lower the energy at which the amplitudes violate partial-wave unitarity, rendering the theory inconsistent. We have performed the first calculation of the 2 à 2 scattering amplitudes for longitudinal spin-2 KK modes and shown that, contrary to claims in the literature, an intricate web of cancellations reduces the overall growth rate of the scattering amplitudes to being merely linear in s, as consistent with the behavior of 5D gravity. This holds both in theories based on a flat extra dimension and those, like Randall-Sundrum models, with a warped extra dimension. We have also demonstrated how to encode the conditions responsible for the cancellations as sum rules relating the couplings of the different KK states. This provides a more intuitive understanding of why some of the cancellations occur and highlights some key differences between theories with flat and warped extra dimensions. Our talk will summarize this work and indicate further directions for exploration.
