Search for Anomalous Couplings in the Higgs Sector at LEP

TL;DR

This study searches for signs of anomalous Higgs boson couplings at LEP across various production and decay channels, setting limits on these couplings and decay rates due to no observed deviations from the Standard Model.

Contribution

It provides the first comprehensive search for anomalous Higgs couplings in multiple channels at LEP, establishing new limits on these couplings and decay rates.

Findings

No evidence for anomalous Higgs production or decay was observed.

Limits were set on anomalous couplings d, db, Delta(g1z), Delta(kappa_gamma), and xi^2.

Constraints on H -> gamma gamma and H -> Z gamma decay rates were established.

Abstract

Anomalous couplings of the Higgs boson are searched for through the processes e^+ e^- -> H gamma, e^+ e^- -> e^+ e^- H and e^+ e^- -> HZ. The mass range 70 GeV < m_H < 190 GeV is explored using 602 pb^-1 of integrated luminosity collected with the L3 detector at LEP at centre-of-mass energies sqrt(s)=189-209 GeV. The Higgs decay channels H -> ffbar, H -> gamma gamma, H -> Z\gamma and H -> WW^(*) are considered and no evidence is found for anomalous Higgs production or decay. Limits on the anomalous couplings d, db, Delta(g1z), Delta(kappa_gamma) and xi^2 are derived as well as limits on the H -> gamma gamma and H -> Z gamma decay rates.