Composite Higgs Sketch

TL;DR

This paper explores how an additional spin 1 triplet of rho particles in composite Higgs models affects unitarity and phenomenology, notably enhancing the Higgs di-photon rate and remaining consistent with current LHC bounds.

Contribution

It introduces the role of a spin 1 custodial triplet in composite Higgs models and analyzes its impact on unitarity constraints and collider phenomenology.

Findings

Perturbative unitarity constrains rho and Higgs couplings.

The rho triplet can significantly boost the Higgs di-photon decay rate.

Current LHC data allows rho masses between 700 GeV and 2 TeV.

Abstract

The coupling of a composite Higgs to the standard model fields can deviate substantially from the standard model values. In this case perturbative unitarity might break down before the scale of compositeness is reached, which would suggest that additional composites should lie well below this scale. In this paper we account for the presence of an additional spin 1 custodial triplet of rhos. We examine the implications of requiring perturbative unitarity up to the compositeness scale and find that one has to be close to saturating certain unitarity sum rules involving the Higgs and the rho couplings. Given these restrictions on the parameter space we investigate the main phenomenological consequences of the spin 1 triplet. We find that they can substantially enhance the Higgs di-photon rate at the LHC even with a reduced Higgs coupling to gauge bosons. The main existing LHC bounds arise from di-boson searches, especially in the experimentally clean channel where the charged rhos decay to a W-boson and a Z, which then decay leptonically. We find that a large range of interesting parameter space with 700 GeV < m(rho) < 2 TeV is currently experimentally viable.