Higgs Production and Decay via e^+e^-rightarrow Z⁰ H⁰ rightarrow bbar bW^+W^- and Irreducible Backgrounds at the Next Linear Collider

The complete matrix element for $e^+e^-\ar b\bar bW^+W^-$ has been computed at tree--level and applied to $Z^0H^0$ production followed by $Z^0\ar b\bar b$ and $H^0\ar W^+W^-$, keeping into account all irreducible backgrounds, which are dominated by \ttb production, at the Next Linear Colliders. We find that, depending on the center of mass energies and on the search strategies, this channel can be useful for the study of the parameters of the Standard Model Higgs boson over the most part of the heavy mass range.