Anomalous gluon-top quark-anti-top quark coupling in single-lepton top-antitop quark events from proton-antiproton collisions at center of mass energy = 1.8 TeV.

摘要

Using the effective Lagrangian formulation with the requirements of Standard Model SU(3)xSU(2)xU(1) symmetries, the leading order effects of new physics at an energy scale &Lgr; on the gtt¯ vertex can be shown to be determined by the strengths of three anomalous couplings CtG, CqG and C tG&phis;. Applying a method designed to utilize the full kinematic information of an event on the top-quarks collected from pp¯ collisions at s =1.8 TeV by the DO experiment during Run I of the Fermilab Tevatron, we have measured CqGL2 = 2.84 +/- 1.78(stat) +/- 0.88(syst), where &Lgr; is set to be 1 TeV and the other two couplings are assumed zero. This is the first direct measurement of gtt¯ coupling and the result is consistent with the Standard Model prediction of zero.