The Higgs boson mixes with an SU(2) septet representation

TL;DR

This paper explores a model where the Higgs boson mixes with an SU(2) septet, affecting electroweak symmetry breaking and Higgs signals at the LHC, while remaining consistent with precision data.

Contribution

It introduces a Higgs sector with an SU(2) septet, analyzing its effects on Higgs couplings, electroweak parameters, and collider phenomenology.

Findings

Enhanced diphoton and gauge boson decay signals at LHC.

Constraints on the septet VEV from electroweak precision tests.

Bounds on additional Higgs boson masses from current data.

Abstract

We study a possibility of the Higgs boson, which consists of an SU(2) doublet and a septet. The vacuum expectation value of a septet with hypercharge Y=2 is known to preserve the electroweak rho parameter unity at the tree level. Therefore, the septet can give significant contribution to the electroweak symmetry breaking. Due to the mixing with the septet, the gauge coupling of the standard-model-like Higgs boson is larger than that in the standard model. We show the sizable VEV of the Higgs septet can be allowed under the constraint from the electroweak precision data. The signal strengths of the Higgs boson for the diphoton and a pair of weak gauge boson decay channels at the LHC are enhanced, while those for the fermonic decay modes are suppressed. The mass of additional neutral Higgs boson is also bounded by the current LHC data for the standard model Higgs boson. We discussed the phenomenology of the multiply charged Higgs bosons, which come from the septet.