Have We Observed the Higgs (Imposter)?

TL;DR

This paper analyzes the nature of the new particle observed at the LHC, evaluating various scalar models and finding that a Higgs doublet best fits the data, while other models are disfavored.

Contribution

It systematically constrains scalar possibilities for the observed particle using electroweak symmetry and LHC data, favoring the Higgs doublet hypothesis.

Findings

Dilaton and singlet imposters are disfavored by data.

Higgs doublet provides the best fit to observed event rates.

Triplet imposter shows some tension with measurements.

Abstract

We interpret the new particle at the Large Hadron Collider as a CP-even scalar and investigate its electroweak quantum number. Assuming an unbroken custodial invariance as suggested by precision electroweak measurements, only four possibilities are allowed if the scalar decays to pairs of gauge bosons, as exemplified by a dilaton/radion, a non-dilatonic electroweak singlet scalar, an electroweak doublet scalar, and electroweak triplet scalars. We show that current LHC data already strongly disfavor both the dilatonic and non-dilatonic singlet imposters. On the other hand, a generic Higgs doublet give excellent fits to the measured event rates of the newly observed scalar resonance, while the Standard Model Higgs boson gives a slightly worse overall fit due to the lack signal in the tau tau channel. The triplet imposter exhibits some tension with the data. The global fit indicates the enhancement in the diphoton channel could be attributed to an enhanced partial decay width, while the production rates are consistent with the Standard Model expectations. We emphasize that more precise measurements of the ratio of event rates in the WW over ZZ channels, as well as the event rates in b bbar and tau tau channels, are needed to further distinguish the Higgs doublet from the triplet imposter.