We consider the pair production of vector-like down-type quarks in an E 6 motivated model, where each of the produced down-type vector-like quark decays into an ordinary Standard Model light quark and a singlet scalar. Both the vector-like quark and the singlet scalar appear naturally in the E 6 model with masses at the TeV scale with a favorable choice of symmetry breaking pattern. We focus on the non-standard decay of the vector-like quark and the new scalar which decays to two photons or two gluons. We analyze the signal for the vector-like quark production in the 2γ + ≥ 2 j channel and show how the scalar and vectorlike quark masses can be determined at the Large Hadron Collider.
The resonant excesses around 2 TeV reported by the ATLAS Collaboration can be explained in the left-right model, and the tight constraints from lepton plus missing energy searches can be evaded if the SU (2) R gauge symmetry is leptophobic. We for the first time propose an anomaly free leptophobic left-right model with gauge symmetry SU (3) C × SU (2) L × SU (2) R × U (1) X where the SM leptons are singlets under SU (2) R . The gauge anomalies are cancelled by introducing extra vector-like quarks. The mass of Z gauge boson, which cannot be leptophobic, is assumed to be around or above 2.5 TeV so that the constraint on dilepton final state can be avoided. Moreover, we find that the W → W Z channel cannot explain the ATLAS diboson excess due to the tension with the constraint on W → jj decay mode. We solve this problem by considering the mixings between the SM quarks and vector-like quarks. We show explicitly that the ATLAS diboson excess can be explained in the viable parameter space of our model, which is consistent with all the current experimental constraints.
Recent results from the experimental collaborations at LHC give hints of a resonance in the diphoton channel at an invariant mass of 750 GeV. We show that such a scalar resonance would be possible in an U (1) extension of the SM where the extended symmetry is hidden and yet to be discovered. We explore the possibilities of accommodating this excess by introducing a minimal extension to the matter content and highlight the parameter space that can accommodate the observed diphoton resonance in the model. The model also predicts new interesting signals that may be observed at the current LHC run.
We propose that the diphoton resonance signal indicated by the recent LHC data might also arise from the pair productions of vector-like heavy down-type quarks with mass around 750 GeV and above. The vector-like quark decays into an ordinary light quark and a Standard Model singlet scalar. The subsequent decay of scalar singlet produces the diphoton excess. Both the vector-like quark and singlet scalars appear naturally in the E 6 , and their masses can be in the TeV scale with a suitable choice of symmetry breaking pattern. The prediction of such a proposal would be to see an accompanying dijet signal at the same mass with similar cross section in the 2γ + 2j final state and two dijet resonances at the same mass for a 4j final state with a cross section, about 100 times larger. Both predictions can be tested easily as the luminosity accumulates in the upcoming runs of the LHC.
We consider vector-like quarks in a leptophobic 221 model characterized by the gauge group SU (2) L × SU (2) 2 × U (1) X , where the SU (2) 2 is leptophobic in nature. We discuss about the pattern of mixing between Standard Model quarks and vector-like quarks and how we prevent tree level flavour-changing interactions in the model. The model also predicts tauphilic scalars decaying mostly to tau leptons. We consider a typical signal of the model in the form of pair production of top-type vector-like quarks which decays to the tauphilic scalars and a third generation quark. We analyze the resulting final state signal for the 13 TeV LHC, containing ≥ 3j(1b) + ≥ 2τ + ≥ 1l and discuss the discovery prospects of such vector-like quarks with non-standard decay modes.
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