Decay-mode independent searches for new scalar bosons with OPAL

TL;DR

This paper reports on topological searches for new scalar bosons produced with a Z boson at LEP energies, setting model-independent upper limits on their production cross sections across various decay modes and mass scenarios.

Contribution

It introduces decay-mode independent search techniques for scalar bosons, including scenarios with broad or multiple close-in-mass states, extending previous Higgs searches.

Findings

No signal observed in the data.

Upper limits set on the production cross section of scalar bosons.

Results applicable to a wide range of decay modes and mass distributions.

Abstract

Topological searches for neutral scalar bosons S0 produced in association with a Z0 boson via the Bjorken process e+e- to SZ at centre-of-mass energies of 91GeV and 183-209GeV are described. These searches are based on studies of the recoil mass spectrum of Z to electrons or muons, and on a search for SZ with Z to neutrinos and S to e+e- or photons. They cover the decays of the S into an arbitrary combination of hadrons, leptons, photons and invisible particles as well as the possibility that it might be stable. No indication for a signal is found in the data and upper limits on the cross section of the Bjorken process are calculated. Cross-section limits are given in terms of a scale factor k with respect to the SM cross section for the Higgs-strahlung process e+e- to HZ. These results can be interpreted in general scenarios independently of the decay modes of the S. The examples considered here are the production of a single new scalar particle with a decay width smaller than the detector mass resolution, and for the first time, two scenarios with continuous mass distributions, due to a single very broad state or several states close in mass.