A measurement of the t- -> m-nmnt branching ratio.

The t- -> m-nmnt branching ratio was measured using data collected from 1990 to 1995 by the OPAL detector at the LEP collider. The resulting value of B(t- -> m-nmnt) = 0.1734 +- 0.0009(stat)+-0.0006(syst) was used in conjunction with other OPAL measurements to test lepton universality, yielding the coupling const. ratios gm/ge = 1.0005 +- 0.0044 and gt/ge = 1.0031 +- 0.0048, in good agreement with the Std. Model prediction of unity. A value for the Michel parameter h = 0.004 +- 0.037 also was detd. and used to find a limit for the mass of the charged Higgs boson, mH+- >1.28tanb, in the Minimal Supersym. Std. Model. [on SciFinder (R)]