Eur. Phys. J. C

**19**, 57-76

DOI: 10.1007/s100520100589

## The heavy neutral Higgs signature in the process

**G.J. Gounaris**

^{1}, P.I. Porfyriadis^{1}and F.M. Renard^{2}^{1}Department of Theoretical Physics, Aristotle University of Thessaloniki, 54006, Thessaloniki, Greece

^{2}Physique Mathématique et Théorique, UMR 5825, Université Montpellier II, 34095 Montpellier Cedex 5, France

(Received: 20 October 2000 / Revised version: 5 January 2001 / Published online: 23 February 2001 -© Springer-Verlag 2001)

** Abstract **

If the standard model (SM) Higgs particle
is sufficiently heavy, then its contribution to
should be largely imaginary, interfering with the also
predominantly imaginary SM "background"generated
by the *W* loop. For standard model
Higgs masses in the region
GeV,
this interference is found to be constructive and
increasing the Higgs signal.
In the minimal SUSY case an interference effect
should also appear for the contribution of the heavier
*CP*-even neutral Higgs boson *H*^{0}, provided it is sufficiently
heavy. The effect is somewhat reduced, though,
by the smallness of the *H*^{0} width and the
and
*ZZ*
branching ratios. The interference is again found to be
constructive
for part of the parameter space corresponding to sfermion
masses at the TeV scale and maximal stop mixing.
For both the SM and the SUSY case, regions of the parameter space
exist, though, where the interference may be destructive.
It is therefore essential to take these effects into account
when searching for possible scalar
Higgs-like candidates. To this aim, we present the complete
analytic expressions for both resonance and background
amplitudes.

**©**

*Società Italiana di Fisica, Springer-Verlag 2001*