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Title: Do color-neutral top partners, as in Twin Higgs models, exist?
Plain: Some proposals keep the Higgs light with partner particles that do not feel the strong force, so the LHC barely produces them. They would show up as small shifts in Higgs couplings, or as Higgs decays to hidden-sector particles that fly a measurable distance before decaying.
Precise: In neutral-naturalness models (Twin Higgs, folded supersymmetry, quirky little Higgs) the top-loop contribution to $m_h^{2}$ is cancelled by states without SM color, with a mirror-sector scale f; Higgs couplings shift by about $v^{2}/(2 f^{2})$ and the Higgs can decay to mirror glueballs with displaced vertices (approximate relations, model dependent). Determine whether such a sector exists with $f\ \text{below about}\ 1\ \text{to}\ 2\ \mathrm{TeV}$, by measuring $\mathrm{BR}(h \to \text{mirror hadrons})$ down to about $1e-4$ and Higgs couplings at the per-mille level, or exclude it.
Settled by: Displaced-vertex searches for exotic Higgs decays at the HL-LHC and at dedicated long-lived-particle detectors, together with per-mille Higgs coupling measurements at a Higgs factory.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: open
Status note: No exotic Higgs decays to long-lived particles observed through LHC Run 2; Batell, Low, Neil and Verhaaren review the open parameter space (Physics Reports 1165, 2026, arXiv:2203.05531).
Posed since: 2005