Diboson excess in the Higgs singlet and vector-like quark models

Abstract

Diboson resonance with mass of $1.8-2$ TeV is reported successively by CMS and ATLAS experiments in proton-proton collisions at $\sqrt{s}=8$ TeV. We investigate the potentiality of Higgs singlet as the TeV resonance. The challenges of low production cross section and high width for a fundamental scalar could be got over by three factors: (1) larger Yukawa couplings, (2) larger number of heavy quarks and (3) smaller mixing angle with standard model Higgs. We find that the required factors could be realized in the framework of two vector-like triplet quarks (VLTQs) and the resulting production cross section and decay fraction of heavy Higgs $\sigma(pp\to H )\times {\rm BR}(H\to W^+ W^- + ZZ)$ can be of ${\cal O}(10)$ fb when masses of new heavy quarks are 1 TeV, the values of Yukawa couplings are around $3$ and the mixing angle is $\sin\theta \sim 0.11$. Furthermore, we study the product of VLTQ-pair production cross section and the BRs of VLTQ decays, and find that the cross sections in the decay channels, such as $u_{4,5} \to b W^+$, $d_5 \to t W^-$ and $d_4 \to b h(Z)$ could be $7-17$ fb at 13 TeV LHC.