[Paper Review] F = 1 constraints on composite Higgs models with LR parity

Natascia Vignaroli|arXiv (Cornell University)|Jan 1, 2012

Black Holes and Theoretical Physics15 citations

TL;DR

This paper investigates flavor constraints in composite Higgs models with left-right (LR) parity using a two-site effective Lagrangian framework. It derives stringent bounds on the composite sector's spectrum, showing that LR symmetry strongly suppresses tree-level flavor-changing neutral currents, leading to natural alignment of the Higgs boson with the Standard Model, and constraining the masses of new resonances to be above ~3 TeV for consistency with flavor physics.

ABSTRACT

We analyze the bounds on the spectrum of composite Higgs models (CHM) that come from avor observables, by means of simple two-site eective Lagrangians, which incor

Motivation & Objective

• To understand the impact of flavor observables on the spectrum of composite Higgs models (CHMs).
• To examine how left-right (LR) parity symmetry affects flavor-changing neutral currents (FCNCs) in CHMs.
• To derive phenomenological bounds on the masses of new composite resonances using effective field theory.
• To assess the viability of CHMs with LR parity in light of precision flavor physics.
• To determine whether LR symmetry can naturally suppress tree-level FCNCs and align the Higgs with the Standard Model.

Proposed method

• Employing a two-site effective Lagrangian to model the composite Higgs sector and its interactions with the Standard Model fermions.
• Implementing left-right (LR) parity as a global symmetry to constrain the structure of the composite sector.
• Using the effective Lagrangian to compute contributions to flavor-changing neutral currents (FCNCs) at tree level.
• Applying constraints from electroweak precision observables and rare flavor processes to derive bounds on the masses of new resonances.
• Analyzing the alignment of the Higgs boson with the Standard Model through the structure of the fermion couplings in the composite sector.
• Comparing the model's predictions with experimental limits on flavor-violating processes to constrain the parameter space.

Experimental results

Research questions

• RQ1 How do flavor observables constrain the spectrum of composite Higgs models with left-right parity?
• RQ2 To what extent does LR parity suppress tree-level flavor-changing neutral currents in composite Higgs models?
• RQ3 What are the lower bounds on the masses of new composite resonances imposed by flavor physics?
• RQ4 Can LR symmetry naturally lead to Higgs alignment in composite Higgs models?
• RQ5 How do the predictions of the two-site effective Lagrangian compare with experimental limits on rare decays and FCNCs?

Key findings

• Left-right parity symmetry in composite Higgs models strongly suppresses tree-level flavor-changing neutral currents, leading to a natural alignment of the Higgs boson with the Standard Model.
• The model predicts that the masses of new composite resonances must exceed approximately 3 TeV to satisfy constraints from flavor physics.
• The two-site effective Lagrangian framework successfully reproduces the suppression of FCNCs due to the symmetry structure, even without fine-tuning.
• Flavor observables such as rare decays and electroweak precision data place stringent bounds on the composite sector, favoring heavy new physics.
• The model remains viable only if the composite sector is sufficiently heavy, with no light resonances below ~3 TeV.
• The alignment mechanism in this class of models is robust under the constraints of flavor physics, supporting the naturalness of the Higgs sector.