D-terms, Unification, and the Higgs Mass

148 citations (145 excluding self-citations). Addressed a central tension in supersymmetry: how to raise the Higgs mass above the LEP bound without fine-tuning, while preserving gauge coupling unification.

The Problem

In the MSSM, the tree-level Higgs mass is bounded by M_Z ~ 91 GeV. Reaching the LEP lower bound of 114 GeV (and ultimately the observed 125 GeV) requires large radiative corrections from heavy stop squarks, which reintroduces fine-tuning — the very problem supersymmetry was supposed to solve. Non-decoupling D-terms from extended gauge symmetries can raise the tree-level bound, but the question was whether this could be done while preserving the successful MSSM prediction of gauge coupling unification.

The Key Idea

The paper shows that unification constrains the structure of gauge extensions tightly: only certain extensions are compatible with the measured coupling constants converging at a single scale. Within these allowed extensions, non-decoupling D-terms raise the Higgs mass to at most ~150 GeV. The extended gauge symmetry must be broken at a few TeV, predicting new heavy gauge bosons accessible to the LHC. The Higgs mass prediction of ≤ 150 GeV turned out to be consistent with the observed 125 GeV discovery eight years later.

Recollections

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• DOI
• arXiv:hep-ph/0409127
• INSPIRE