Flavour Independent hA Search and Two Higgs Doublet Model Interpretation of Neutral Higgs Boson Searches at LEP

TL;DR

This paper presents a flavour-independent search for neutral Higgs bosons at LEP, setting limits on the Two Higgs Doublet Model parameters by analyzing combined data from LEP1 and LEP2, and excluding significant regions of the model's parameter space.

Contribution

It introduces a new flavour-independent method for Higgs boson searches and provides comprehensive constraints on the 2HDM(II) parameter space using combined LEP data.

Findings

Excluded large regions of 2HDM(II) parameter space at 95% CL.

Set upper limits on cross-sections for Higgs pair-production.

Identified specific mass ranges for Higgs bosons that are excluded.

Abstract

Upper limits on the cross-section of the pair-production process e+e- -> h0A0 assuming 100% decays into hadrons, are derived from a new search for the h0A0 -> hadrons topology, independent of the hadronic flavour of the decay products. Searches for the neutral Higgs bosons h0 and A0, are used to obtain constraints on the Type II Two Higgs Doublet Model (2HDM(11)) with no CP violation in the Higgs sector and no additional non Standard Model particles besides the five Higgs bosons. The analysis combines LEP1 and LEP2 data collected with the OPAL detctor up to the highest available centre-of-mass energies. The searches are sensitive to the h0, A0 -> qq, gg,tau+tau- and h0 -> A0A0 decay modes of the Higgs bosons. The 2HDM(II) parameter space is explored in a detailed scan. Large regions of the 2HDM(II) parameter space are excluded at the 95% CL in the (mh, mA), (mh, tanb) and (mA, tanb) planes, using both direct neutral Higgs boson searches and indirect limits derived from Standard Model high precision measurements. The region 1 lesssim mh lesssim 55 GeV and 3 lesssim mA lesssim 63 GeV is excluded at 95% CL independently of the choice of the 2HDM(II) parameters.