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

Exploring anomalous top interactions via the final lepton in ttbar productions/decays at hadron colliders

We study momentum distributions of the final-state charged lepton in ppbar/pp --> ttbar --> l^+ X (l=e or mu) at hadron colliders, i.e., Tevatron and Large Hadron Collider (LHC) in order to explore possible new-physics effects in the top-quark sector. Assuming general model-independent ttbar g + ttbar gg and tbW interactions beyond the standard model, we first derive analytical formulas for the corresponding parton-parton processes. We then compute the lepton angular, energy and transverse-momentum distributions in ppbar/pp collisions to clarify how they are affected by those anomalous couplings.Comment: Journal information added. Title slightly changed in the published version (top interaction --> top-quark interaction). One typo in eqs.(15)-(19) corrected (dE_l c_l --> dE_l dc_l

Full analysis of general non-standard tbW couplings

Possible non-standard couplings which could contribute to the t → bW 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

パートン ショウトツ デノ トップ クォーク タイセイセイ ホウカイ ニオケル シュウジョウタイ レプトン ウンドウリョウ ブンプ ト ヒヒョウジュン トップ ソウゴ サヨウ

We study the momentum distributions of the final-state charged lepton in parton-parton collisions q¯q, gg → t¯t → +X ( = e or μ), considering their application to actual experimental-data analyses at high-energy hadron colliders, i.e., Tevatron and Large Hadron Collider (LHC). Assuming general anomalous t¯tg + t¯tgg and tbW couplings, we derive analytical formulas for the above distributions based on Kawasaki-Shirafuji-Tsai formalism. We there take into account all the terms on the former-coupling parameters while up to the linear terms about the latter. We then calculate the lepton energy- and angular-distributions to clarify how they are affected by the anomalous couplings, and also search, through the total cross sections, for the parameter range where quadratic (or higher-order) terms of nonstandard QCD couplings can safely be neglected and consequently we can carry out the optimal-observable analysis properly for estimating the expected statistical uncertainties in parameter measurements