Speaker: Xiaochuan Lu
Title: Effective Field Theories: Truncation, Validity, and Uncertainty
Room: 3024
Zoom: https://zoom.us/j/186024391
Host: Luty
Abstract: The application of SMEFT for motivating and interpreting LHC searches has received growing attention in recent years. Despite numerous technical and practical developments, currently there is still no consensus regarding how to address the issues of validity and uncertainties associated with the SMEFT truncation in operator dimension. Establishing a prescription for how to use SMEFT at the LHC is of paramount importance. In this talk, I present a new approach that takes a small step toward this goal. Working with a toy case, we demonstrate that when the search channel is sufficiently inclusive in terms of the energy of the final state particles, an EFT description could still be valid even when the new physics scale is significantly below the center of mass energy at the LHC, due to the proper inclusion of PDF effects. This observation can be applied to modify the standard perturbative partial wave unitarity conditions to understand the question of EFT validity from the bottom up.
Abstract: We discuss a class of higher-derivative, Lee-Wick quantum field theories that form a sequence whose limit point is a ghost-free, nonlocal theory. As the limit point is approached, these theories develop an emergent nonlocal scale that regulates loop diagrams and remains hierarchically smaller than the lightest Lee-Wick partner state. We discuss the possible relevance of these theories to addressing the hierarchy problem.
