The Effect of Composite Resonances on Higgs decay into two photons

TL;DR

This paper investigates how heavy composite particles in strongly coupled electroweak models affect Higgs decay to two photons, deriving constraints on composite masses from LHC data and electroweak precision tests.

Contribution

It introduces an effective chiral Lagrangian framework to analyze composite effects on Higgs decay and constrains composite masses using LHC and electroweak data.

Findings

Composite vector and axial-vector masses are constrained to specific TeV ranges.

Non-standard kinetic mixing is necessary for consistency with experimental data.

Higgs to gamma gamma decay provides significant bounds on composite models.

Abstract

In scenarios of strongly coupled electroweak symmetry breaking, heavy composite particles of different spin and parity may arise and cause observable effects on signals that appear at loop levels. The recently observed process of Higgs to $\gamma \gamma$ at the LHC is one of such signals. We study the new constraints that are imposed on composite models from $H\to \gamma\gamma$, together with the existing constraints from the high precision electroweak tests. We use an effective chiral Lagrangian to describe the effective theory that contains the Standard Model spectrum and the extra composites below the electroweak scale. Considering the effective theory cutoff at $\Lambda = 4\pi v \sim 3 $ TeV, consistency with the $T$ and $S$ parameters and the newly observed $H\to \gamma\gamma$ can be found for a rather restricted range of masses of vector and axial-vector composites from $1.5$ TeV to $1.7$ TeV and $1.8$ TeV to $1.9$ TeV, respectively, and only provided a non-standard kinetic mixing between the $W^{3}$ and $B^{0}$ fields is included.