Nonstandard Higgs Boson Decays

TL;DR

This review discusses nonstandard Higgs decays involving hidden sector particles, which can evade traditional mass limits and alleviate fine-tuning issues in BSM theories, especially supersymmetry.

Contribution

It provides a comprehensive overview of nonstandard Higgs decay phenomenology and highlights their implications for Higgs mass constraints and BSM model building.

Findings

Nonstandard decays can allow a Higgs below 114 GeV.

Such decays can resolve fine-tuning problems in supersymmetry.

They are compatible with precision electroweak data.

Abstract

This review summarizes the motivations for and phenomenological consequences of nonstandard Higgs boson decays, with emphasis on final states containing a pair of non-Standard-Model particles that subsequently decay to Standard Model particles. Typically these non-Standard-Model particles are part of a ``hidden'' sector, for example a pair of neutral Higgs bosons or a pair of unstable neutralinos. We emphasize that such decays allow for a Higgs substantially below the Standard Model Higgs LEP limit of 114 GeV. This in turn means that the ``fine-tuning'' problems of many Beyond the Standard Model (BSM) theories, in particular supersymmetric models, can be eliminated while achieving excellent consistency with precision electroweak data which favor a Higgs boson with mass below $100\gev$ and standard $WW$, $ZZ$, and top couplings.