Heavy Higgs production and decay via $e^{+}{e}^{-}\to Z^0{H}^0\to b\bar{b}{Z}^0{Z}^0$ and irreducible backgrounds at Next Linear Colliders

Abstract

The complete matrix element for $e^+e^-\ar b\bar bZ^0Z^0$ has been computed at tree--level and applied to $Z^0{H}^0$--production followed by $Z^0\ar b\bar b$ and $H^0\ar Z^0Z^0$, including all the irreducible background, at Next Linear Colliders. We find that, assuming flavour identification of the $Z^0$--decay products, this channel, together with $e^+e^-\ar b\bar bW^+W^-$ in which $Z^0H^0\ar (b\bar b)(W^+W^-$), can be important for the study of the parameters of the Standard Model Higgs boson over the heavy mass range $2M_{Z^0}\Ord M_{H^0}\Ord 2{m_t}$.

24 pages, LaTeX (uses Feynman), 7 figures (.ps files or hardcopies of figs.2-7 available upon request)