- The paper develops an effective field theory that extends CP-even operators to describe a light dynamical Higgs as a quasi-Goldstone boson.
- It employs a ξ = (v/f)² expansion to systematically connect the linear Standard Model framework with non-linear electroweak symmetry breaking scenarios.
- The proposed taxonomy of 26 CP-even operators provides a practical basis for identifying exotic gauge-Higgs couplings in collider experiments.
Overview of the Effective Chiral Lagrangian for a Light Dynamical "Higgs Particle"
The research paper focuses on the formulation of a comprehensive set of operators for a light dynamical Higgs particle within a framework of chiral effective field theories. The analysis extends the CP-even chiral effective operators accounting for the presence of a light Higgs-like scalar, which is treated as a dynamical quasi-Goldstone boson from a spontaneously broken larger symmetry group. This work serves to bridge the gap between linear realizations of the electroweak symmetry breaking mechanism, epitomized by the Standard Model (SM), and non-linear realizations that incorporate a light Higgs-like entity.
Theoretical Context
A quintessential problem within the field of theoretical particle physics is understanding the dynamics underlying electroweak symmetry breaking (EWSB). The existence of a new resonance at the electroweak scale, consistent with the characteristics of the SM Higgs boson, motivates the exploration of this symmetry breaking sector beyond the hypothesis of a fundamental, elementary SM Higgs. In phenomenological models proposing a composite Higgs boson, which maintains a light mass due to its nature as a quasi-Goldstone boson, there is a pronounced need to scrutinize the existence of exotic gauge-Higgs couplings. This paper aims to address this by outlining an effective Lagrangian approach encompassing chiral expansions with up to four derivative operators.
Methodological Approach
The authors employ an effective field theory (EFT) framework, categorizing operators based on the inherent degree of non-linearity encoded by the parameter ξ = (v/f)², where v is the electroweak scale and f represents the scale associated with new, strong dynamics. Various limit scenarios are considered, ranging from the linear SM picture to the fully non-linear regime, allowing for significant theoretical flexibility. The analysis includes both gauge and gauge-Higgs operators up to four derivatives, focusing on their interplay with the SM fields.
A comprehensive list of 26 CP-even operators is proposed, delineating their ξ-dependence to ensure clarity in practitioner applications. This effectively extends the basis from previous works to include the interactions pertinent to a light Higgs scalar in potentially non-linear regimes. Such interplay is essential for understanding deviations from SM predictions in experimental data, particularly in high-energy physics scenarios explored by LHC experiments.
Results and Implications
The paper yields a detailed taxonomy of operators needed to describe exotic Higgs behavior within strong interaction contexts, effectively closing gaps suggested by earlier model-dependent analyses. Additionally, the operators' coefficients and functional dependencies provide a systematic basis for scrutinizing Higgs interactions beyond the customary Yukawa couplings and traditional perturbative expansions.
From a theoretical standpoint, the application of this comprehensive operator set facilitates a nuanced exploration of EWSB mechanisms, notably in identifying novel gauge-Higgs couplings and their experimental implications. Experimentally, the derived operators can guide searches for deviations in Higgs sector interactions at current and future collider experiments. The framework can also serve as a pivotal model-independent approach in developing phenomenological strategies for BSM Higgs sectors, particularly those that exhibit composite or holographic characteristics.
Concluding Thoughts
The presented work significantly contributes to the domain of particle physics by advancing the understanding of effective chiral Lagrangians, especially in contexts where a light Higgs-like particle is proposed to operate under strong dynamics. Future research directions could explore these operators' phenomenological implications, perhaps leveraging this framework for precision measurements in collider physics and advancing the discourse on the fundamental nature of the Higgs boson within new physics paradigms.
