DOI 10.1007/s100529900050
Restoring good high energy behaviour in Higgs production via W fusion at the LHC
K. Philippides1 - W.J. Stirling1,2
1 Department of Physics, University of Durham,
Durham, DH1 3LE, UK
2 Department of Mathematical Sciences, University of Durham, Durham,
DH1 3LE, UK
Received: 30 January 1999 / Published online: 20 May 1999
Abstract
The W-fusion scattering process
for off-shell W bosons
is studied, focusing on the issue of its high-energy behaviour
which is known to be anomalous. It is shown that the unitarity violating
terms can be isolated and extracted in a well-defined and efficient
way using the pinch- technique.
This restores the good high energy behaviour of the cross section
and, in particular,
makes possible the identification of the Higgs resonance in the invariant
mass distribution mZZ of the Z pair. The discarded terms, which are
proportional to the off-shellness of the W bosons, cancel against similar
terms originating from the remaining diagrams for the full physical
process 
.This cancellation ensures the gauge invariance of our result, which therefore
constitutes a meaningful separation between signal and background
when they both contribute coherently.
Equipped with this result, we are able to define a resonant approximation
for the process 
which circumvents the
problem of good high energy behaviour without having to resort to the
lengthy calculation of the complete set of diagrams.
In this approximation
only the W- and Z-fusion signal
graphs are included, i.e. the ones which
contain the Higgs resonance. We have verified that the
approximate resonant
cross section describes very well the full
result not only close to the resonance but also beyond it.
Copyright Springer-Verlag
