Unitarity violation and the geometry of Higgs EFTs

Cohen, T., Craig, N., Lu, X. and Sutherland, D. (2021) Unitarity violation and the geometry of Higgs EFTs. Journal of High Energy Physics, 2021(12), 3. (doi: 10.1007/JHEP12(2021)003)

Abstract

We derive the scale of unitarity violation from the geometry of Effective Field Theory (EFT) extensions of the Standard Model Higgs sector. The high-energy behavior of amplitudes with more than four scalar legs depends on derivatives of geometric invariants with respect to the physical Higgs field h, such that higher-point amplitudes begin to reconstruct the scalar manifold away from our vacuum. In theories whose low-energy limit can be described by the Higgs EFT (HEFT) but not the Standard Model EFT (SMEFT), non-analyticities in the vicinity of our vacuum limit the radius of convergence of geometric invariants, leading to unitarity violation at energies below 4πv. Our results unify approaches to the HEFT/SMEFT dichotomy based on unitarity, analyticity, and geometry, and more broadly illustrate the sense in which observables probe the geometry of an EFT. Along the way, we provide novel basis-independent results for Goldstone/Higgs boson scattering amplitudes expressed in terms of geometric covariant quantities.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Sutherland, Dr David
• Authors: Cohen, T., Craig, N., Lu, X., and Sutherland, D.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Journal of High Energy Physics
• Publisher: Springer
• ISSN: 1126-6708
• ISSN (Online): 1029-8479
• Published Online: 01 December 2021
• Copyright Holders: Copyright © 2021 The Authors
• First Published: First published in Journal of High Energy Physics 2021(12): 3
• Publisher Policy: Reproduced under a Creative Commons License