Search for Higgs Bosons and Other Massive States decaying into two Photons in e+e- Collisions at 189 GeV

TL;DR

This paper reports a search for heavy scalar and vector bosons decaying into photon pairs in electron-positron collisions at 189 GeV, aiming to identify Higgs bosons and similar particles with enhanced photon decay modes.

Contribution

It presents the first combined analysis of OPAL data at 189 GeV and lower energies to set bounds on Higgs-like particles decaying into photons, including model-independent limits.

Findings

No significant signal observed for Higgs or heavy states decaying into photons.

Established 95% confidence level bounds on production cross-section times branching ratio.

Constraints applied to models with enhanced Higgs to photon decay couplings.

Abstract

A search is described for the generic process e+e- to X Y, where X is a neutral heavy scalar boson decaying into a pair of photons, and Y is a neutral heavy boson (scalar or vector) decaying into a fermion pair. The search is motivated mainly by the cases where either X, or both X and Y, are Higgs bosons. In particular, we investigate the case where X is the Standard Model Higgs boson and Y the Z0 boson. Other models with enhanced Higgs boson decay couplings to photon pairs are also considered. The present search combines the data set collected by the OPAL collaboration at 189 GeV collider energy, having an integrated luminosity of 182.6pb-1, with data samples collected at lower energies. The search results have been used to put 95% confidence level bounds, as functions of the mass of X, on the product of the cross-section and the relevant branching ratios, both in a model independent manner and for the particular models considered.