Single production ofX±5/3andY∓4/3vectorlike quarks at the LHC

다국어 초록 (Multilingual Abstract)

<P>Two triplet vectorlike quarks (VLQs) with hypercharges of Y = 2/3, -1/3 and one singlet scalar boson are embedded in the standard model to resolve the 750 GeV diphoton excess. The constraints on the tree-level Higgs- and Z-mediated flavor-changing neutral currents are discussed in detail. Besides the resolution of excess, it is found that the signal strength of diphoton Higgs decay can have a 10% deviation from the SM prediction and that the upper limits of the branching ratios for rare top-quark decays are BR (t -> c(h, Z)) < (6.8, 0.48) x 10(-5). We find that the production cross section of a single VLQ by electroweak processes is larger than that of a VLQ pair by QCD processes. To explore the signals of the heavy VLQs at the LHC, we thoroughly analyze the production of single X-+/- 5/3 and Y--/+ 4/3 via q(i)q'(j) annihilations in pp collisions at root s = 13 TeV. It is found that the electroweak production cross sections for dX(5/3), uY(-4/3), and dY(4/3) channels with m(X) = m(Y) = 1 TeV can be 84.3, 72.3, and 157.8 fb, respectively, and the dominant decay modes are X-5/3 -> (c, t)W+ and Y-4/3 -> (s, b) W-. With adopting kinematic cuts, the significance for the pp -> dW(+)t channel can be over 5 sigma.</P>