Higgs ultraviolet softening

TL;DR

This paper investigates effective operators affecting Higgs propagator behavior, exploring their implications for new physics sensitivity, and constrains their coefficients using current LHC data, with a focus on both linear and non-linear electroweak symmetry breaking models.

Contribution

It introduces a unified analysis of operators causing Higgs propagator modifications, comparing ghost scalar and equations of motion methods, and applies experimental data to constrain these operators.

Findings

Operators modify Higgs potential and fermionic couplings in linear models.

Anomalous gauge couplings arise in non-linear models.

Current LHC data constrains the operator coefficients effectively.

Abstract

We analyze the leading effective operators which induce a quartic momentum dependence in the Higgs propagator, for a linear and for a non-linear realization of electroweak symmetry breaking. Their specific study is relevant for the understanding of the ultraviolet sensitivity to new physics. Two methods of analysis are applied, trading the Lagrangian coupling by: i) a "ghost" scalar, after the Lee-Wick procedure; ii) other effective operators via the equations of motion. The two paths are shown to lead to the same effective Lagrangian at first order in the operator coefficients. It follows a modification of the Higgs potential and of the fermionic couplings in the linear realization, while in the non-linear one anomalous quartic gauge couplings, Higgs-gauge couplings and gauge-fermion interactions are induced in addition. Finally, all LHC Higgs and other data presently available are used to constrain the operator coefficients; the future impact of $pp\to\text{4 leptons}$ data via off-shell Higgs exchange and of vector boson fusion data is considered as well. For completeness, a summary of pure-gauge and gauge-Higgs signals exclusive to non-linear dynamics at leading-order is included.