Search for Higgs bosons and new particles decaying into two photons at s=183 GeV

A search for the resonant production of high mass photon pairs associated with a leptonic or hadronic system has been performed using a data sample of 57.7 pby1 collected at an average center-of-mass energy of 182.6 GeV with the OPAL detector at LEP. No evidence for contributions from non-Standard Model physics processes was observed. The observed Ž 0 candidates are used to place limits on B H ™gg . assuming a Standard Model production rate for Higgs boson masses up to 92 GeV, and on the production cross section for a scalar resonance decaying into di-photons up to a mass of 170 GeV. Ž .Ž .Ž . q y Upper limits on the product of cross section and branching ratios, s e e ™XY =B X™gg =B Y™ff , as low as 70 fb are obtained over the range 10-MX Y XY -170 GeV for the case where 10-M -160 GeV and M qM )90 GeV, independent of the nature of Y provided it decays to a fermion pair and has negligible width. Higgs scalars which couple only to gauge bosons at Standard Model strength are ruled out up to a mass of 90.0 GeV at the 95% confidence level. Limits are also placed on non-minimal Higgs sectors having triplet representations. q 1998 Published by Elsevier Science B.V. All rights reserved.