Optimal-observable Analysis of Possible Non-standard Top-quark Couplings in pp -> t t-bar X -> l^+ X'

Possible non-standard top-quark interactions with the gluon and the W boson induced by SU(3) X SU(2) X U(1) gauge-invariant dimension-6 effective operators are studied for hadron-collider experiments. Current limits on top-gluon couplings are presented by using the latest experimental data of t t-bar productions at the Tevatron and the Large Hadron Collider (LHC). The optimal-observable procedure is applied to the charged-lepton distributions in p p -> t t-bar X -> l^+ X' (l = e or mu) at the LHC in order to estimate the expected statistical uncertainties in measurements of those non-standard top-gluon and top-W couplings that contribute to this process in the leading order.