Full analysis of general non-standard tbW couplings

Possible non-standard couplings which could contribute to the t -> b W process are studied based on the effective-Lagrangian approach. The corresponding effective Lagrangian consists of four kinds of dimension-6 effective operators, each of which has an independent coupling constant. In this analysis, all those couplings are treated as complex numbers and constraints on them are estimated by using recent experimental data from the LHC. We point out that the resultant constraints on those couplings are still not that strong because contributions from some couplings can work oppositely with each other.Comment: One comment and two related references added. Final version to appear in Phys.Lett.

Final charged-lepton angular distribution and possible anomalous top-quark couplings in p p -> t tbar X -> l^+ X'

Possible anomalous (or nonstandard) top-quark interactions with the gluon and those with the W boson induced by SU(3) x SU(2) x U(1) gauge-invariant dimension-6 effective operators are studied in p p -> t tbar X -> l^+ X' (l=e or mu) at the Large Hadron Collider (LHC). The final charged-lepton (l^+) angular distribution is first computed for nonvanishing nonstandard top-gluon and top-W couplings with a cut on its transverse momentum. The optimal-observable procedure is then applied to this distribution in order to estimate the expected statistical uncertainties in measurements of those couplings that contribute to this process in the leading order.Comment: latex_2e, 14 pages, 4 eps figure