Phenomenology of Electroweak Symmetry Breaking from Theory Space
2/11/2002
362 citations (345 excluding self-citations). The companion paper to the Minimal Moose, translating the theoretical mechanism into concrete predictions for colliders and dark matter experiments.
The Problem
The Minimal Moose paper established the theoretical framework: a two-site moose construction where the Higgs is a pseudo-Goldstone boson protected by collective symmetry breaking. But a mechanism is not a prediction. To test the idea, experimentalists needed to know what new particles appear, at what masses, with what production cross-sections and decay signatures. They also needed to know whether the model was already excluded by precision electroweak measurements from LEP.
The Key Results
The paper works out the full low-energy spectrum: a pair of light Higgs doublets, new weak triplet and singlet scalars, and heavy gauge bosons and vector-like fermions at the TeV scale. Electroweak symmetry breaking is triggered radiatively by the top Yukawa coupling, analogous to radiative EWSB in supersymmetry but without superpartners. The paper identifies the distinctive decay signatures of each new particle and maps out the parameter space consistent with precision electroweak constraints.
One unexpected result was a new dark matter candidate. The model has a discrete geometric symmetry, analogous to R-parity in supersymmetry, under which the lightest new scalar is stable. This made it a viable WIMP candidate, giving the Little Higgs framework a dark matter prediction that supersymmetric models had long used as a selling point.
Impact
The phenomenological predictions in this paper were the basis for much of the subsequent Little Higgs literature. Perelstein, Peskin, and Pierce’s “Phenomenology of the Little Higgs Model” (694 citations) built directly on this work to produce detailed LHC predictions. The dark matter candidate motivated the T-parity construction (578 citations) that improved the model’s compatibility with precision constraints while preserving the stable dark matter particle. The paper is cited alongside the Minimal Moose in the major reviews of Little Higgs physics.
Recollections
This was an immediate follow-up to Nima Arkani-Hamed, Andy Cohen, and Howard Georgi’s initial papers on deconstructing dimensions and electroweak symmetry breaking from dimensional deconstruction. We created the smallest theory we could come up with and worked out the phenomenology in detail. It was my second paper, and there was a real urgency to it — the Little Higgs idea was new and we wanted to establish the phenomenological predictions before others did.
Thomas Gregoire was a fellow student of Nima’s. We were living together in Central Square, Cambridge, after relocating from Berkeley to follow Nima to Harvard. We spent a lot of time thinking about whether the model could produce scalar dark matter from the discrete symmetry of the moose construction. I later pursued the dark matter angle further in a paper with Dan Hooper on scalar dark matter from theory space.