Associated production of a single heavy T quark in the littlest and simplest little Higgs models

The colored SU(2)L-singlet heavy T-quark is one of the most crucial ingredients in little Higgs models, which is introduced to cancel the largest contribution of the standard model (SM) top quark to the Higgs boson mass at one-loop level. In two representative little Higgs models, the littlest Higgs model and the SU(3) simplest Higgs model, we comprehensively study the single heavy T-quark production at Large Hadron Collider (LHC). After presenting the possibility of relatively light (∼500GeV) T-quark in the simplest little Higgs model, we consider all the relevant processes, the 2→2 process of qb→q′T, the 2→3 process of qg→q′Tb̄, the s-channel process of qq̄′→Tb̄, and the gluon-fusion process of gg→Tt̄. We found that the 2→3 process can be quite important, as its cross section is about 30% of the 2→2 one and it is dominant in high pT distributions. The s-channel and the gluon-fusion processes also show distinctive features in spite of their suppressed cross sections. In the gluon-fusion process of the simplest little Higgs model, for example, the pseudoscalar contribution is rather dominant over the Higgs contribution for relatively light MT.