119110337
Further study of an approach to the unification of gauge symmetries in theories with dynamical symmetry breaking
We extend to larger unification groups an earlier study exploring the possibility of unification of gauge symmetries in theories with dynamical symmetry breaking. Based on our results, we comment on the outlook for models that seek to achieve this type of unification.
119072370
LHC signatures of two-Higgs-doublets with fourth family
A bstractOn-going Higgs searches in the light mass window are of vital importance for testing the Higgs mechanism and probing new physics beyond the standard model (SM). The latest ATLAS and CMS searches for the SM Higgs boson at the LHC (7 TeV) found some intriguing excesses of events in the γγ/VV* channels (V = Z, W) around the mass-range of 124–126 GeV. We explore a possible explanation of the γγ and VV* signals from the light CP-odd Higgs A0 or CP-even Higgs h0 from the general two-Higgs-doublet model with fourth-family fermions. We demonstrate that by including invisible decays of the Higgs boson A0or h0to fourth-family neutrinos, the predicted γγ and VV* signals can explain the observed new signatures at the LHC, and will be further probed by the forthcoming LHC runs in 2012.
119248663
LHC Higgs signatures from extended electroweak gauge symmetry
A bstractWe study LHC Higgs signatures from the extended electroweak gauge symmetry SU(2) ⊗ SU(2) ⊗ U(1). Under this gauge structure, we present an effective UV completion of the 3-site moose model with ideal fermion delocalization, which contains two neutral Higgs states (h, H) plus three new gauge bosons (W′, Z′). We study the unitarity, and reveal that the exact E2 cancellation in the longitudinal VLVL scattering amplitudes is achieved by the joint role of exchanging both spin-1 new gauge bosons W′/Z′ and spin-0 Higgs bosons h/H. We identify the lighter Higgs state h with mass 125 GeV, and derive the unitarity bound on the mass of heavier Higgs boson H. The parameter space of this model is highly predictive. We study the production and decay signals of this 125 GeV Higgs boson h at the LHC. We demonstrate that the h Higgs boson can naturally have enhanced signals in the diphoton channel gg → h → γγ, while the event rates in the reactions gg → h → W W∗ and gg → h → ZZ∗ are generally suppressed relative to the SM expectation. Searching the h Higgs boson via the associated production and the vector boson fusions are also discussed for our model. We further analyze the LHC signals of the heavier Higgs boson H as a new physics discriminator from the SM. For wide mass-ranges of H, we derive constraints from the existing LHC searches, and study the discovery potential of H at the LHC (8 TeV) and LHC (14 TeV).
119239555
Higgsphobic and fermiophobic Z’ as a single dark matter candidate
A bstractA spin-1 Z’ particle as a single dark matter candidate is investigated by assuming that it does not directly couple to the Higgs boson and standard model fermions and does not mix with the photon and Z boson. The remaining dominant vertices are quartic Z′Z′ZZ and Z′Z′W+W−, which can induce effective $ {Z^{\prime }}{Z^{\prime }}q\overline{q} $ couplings through standard-model gauge-boson loops. We discuss constraints from the cosmological thermal relic density, and direct and indirect-detection experiments, and find that a dark Z’ can only exist above the W boson mass threshold, and the effective quartic coupling of Z′Z′VV is bounded in the region of 10−3~10−2.