The process e(+)e(-) --> gamma gamma(gamma) is studied using data recorded
with the OPAL detector at LEP. The data sample taken at a centre-of-mass en
ergy of 189 GeV corresponds to a total integrated luminosity of 178 pb(-1).
The measured cross-section agrees well with the expectation from QED. A fi
t to the angular distribution is used to obtain improved limits at 95% CL o
n the QED cut-off parameters: Lambda(+)> 304 GeV and Lambda(-)> 295 GeV as
well as a mass limit for an excited electron, M-e * > 306 GeV assuming equa
l e*e gamma and ee gamma couplings. Graviton exchange in the context of the
ories with higher dimensions is excluded for scales G(+)< 660 GeV and G(-)<
634 GeV. No evidence for resonance production is found in the invariant ma
ss spectrum of photon pairs. Limits are obtained for the cross-section time
s branching ratio for a resonance decaying into two photons and produced in
association with another photon. (C) 1999 Published by Elsevier Science B.
V. All rights reserved.