Searches for anomalous tqZ couplings from the trilepton signal of tZ associated production at the 14 TeV LHC

We investigate the observability of the top anomalous tqZ couplings via the trilepton signatures at the Large Hadron Collider (LHC) with the center-of-mass energy of 14 TeV. We focus on signals of the tZ associated production with the decay mode t→W+b→bℓ+νℓ, Z→ℓ+ℓ−, and tt¯ production with the decay mode t¯→Z(→ℓ+ℓ−)q¯ and t→bℓ+νℓ, where ℓ=e,μ and q reflects up and charm quarks. It is shown that at 3σ level, the FCNC top quark decay branching ratios can be probed at, respectively, about Br(t→uZ)≤1.3×10−4 and Br(t→cZ)≤4.2×10−4 with the integrated luminosity of 100 fb−1, and probed down to Br(t→uZ)≤2.2×10−5 and Br(t→cZ)≤8×10−5 for the high-luminosity LHC with 3000 fb−1.