UV-Completion by Classicalization

TL;DR

This paper introduces a novel classicalization approach for UV-completion of non-renormalizable theories, where classical objects called classicalons unitarize high-energy scattering amplitudes, with significant implications for the Standard Model and collider phenomenology.

Contribution

It proposes classicalization as a new mechanism for UV-completion, involving classicalons formed by classicalizer fields, applicable to non-gravitational theories like the Standard Model.

Findings

Classicalons can unitarize high-energy scattering amplitudes.

Classicalization applies to Higgsless and Higgs scenarios in the Standard Model.

Distinct experimental signatures are predicted at the LHC.

Abstract

We suggest a novel approach to UV-completion of a class of non-renormalizable theories, according to which the high-energy scattering amplitudes get unitarized by production of extended classical objects (classicalons), playing a role analogous to black holes, in the case of non-gravitational theories. The key property of classicalization is the existence of a classicalizer field that couples to energy-momentum sources. Such localized sources are excited in high-energy scattering processes and lead to the formation of classicalons. Two kinds of natural classicalizers are Nambu-Goldstone bosons (or, equivalently, longitudinal polarizations of massive gauge fields) and scalars coupled to energy-momentum type sources. Classicalization has interesting phenomenological applications for the UV-completion of the Standard Model both with or without the Higgs. In the Higgless Standard Model the high-energy scattering amplitudes of longitudinal $W$-bosons self-unitarize via classicalization, without the help of any new weakly-coupled physics. Alternatively, in the presence of a Higgs boson, classicalization could explain the stabilization of the hierarchy. In both scenarios the high-energy scatterings are dominated by the formation of classicalons, which subsequently decay into many particle states. The experimental signatures at the LHC are quite distinctive, with sharp differences in the two cases.