Searches for invisibly decaying Higgs bosons with the DELPHI detector at LEP

TL;DR

This paper reports on searches for invisibly decaying Higgs bosons at LEP using the DELPHI detector, setting mass limits and exploring implications within MSSM and Majoron models.

Contribution

First search for invisibly decaying Higgs bosons at LEP covering a broad mass range, providing new limits and interpretations within supersymmetric and Majoron models.

Findings

No signal observed for invisibly decaying Higgs bosons.

Mass limit of 112.1 GeV/c^2 at 95% confidence level.

Constraints placed on MSSM and Majoron models.

Abstract

Searches for HZ production with the Higgs boson decaying into an invisible final state were performed using the data collected by the DELPHI experiment at centre-of-mass energies between 188 GeV and 209 GeV. Both hadronic and leptonic final states of the Z boson were analysed. In addition to the search for a heavy Higgs boson, a dedicated search for a light Higgs boson down to 40 GeV/c^2 was performed. No signal was found. Assuming the Standard Model HZ production cross-section, the mass limit for invisibly decaying Higgs bosons is 112.1 GeV/c^2 at 95% confidence level. An interpretation in the Minimal Supersymmetric extension of the Standard Model (MSSM) and in a Majoron model is also given.