Abstract
Confining hidden sectors are an attractive possibility for physics beyond the Standard Model (SM). They are especially motivated by neutral naturalness theories, which reconcile the lightness of the Higgs with the strong constraints on colored top partners. We study hidden QCD with one light quark flavor, coupled to the SM via effective operators suppressed by the mass M of new electroweak-charged particles. This effective field theory is inspired by a new tripled top model of supersymmetric neutral naturalness. The hidden sector is accessed primarily via the Z and Higgs portals, which also mediate the decays of the hidden mesons back to SM particles. We find that exotic Z decays at the LHC and future Z factories provide the strongest sensitivity to this scenario, and we outline a wide array of searches. For a larger hidden confinement scale Λ ∼ O (10) GeV, the exotic Z decays dominantly produce final states with two hidden mesons. ATLAS and CMS can probe their prompt decays up to M ∼ 3 TeV at the high luminosity phase, while a TeraZ factory would extend the reach up to M ∼ 20 TeV through a combination of searches for prompt and displaced signals. For smaller Λ ∼ O (1) GeV, the Z decays to the hidden sector produce jets of hidden mesons, which are long-lived. LHCb will be a powerful probe of these emerging jets. Furthermore, the light hidden vector meson could be detected by proposed dark photon searches.
Highlights
Interact only weakly with the Standard Model (SM) sector
Motivated by a possible realization of the tripled top model for neutral naturalness, we have studied a confining hidden sector where one fermion ψ is light compared to the confinement scale Λ
The latter is taken in the range 0.1 GeV Λ 15 GeV, as generally motivated by 2-loop naturalness considerations
Summary
We present a NN model with a confining hidden sector of light mesons, whose constituents are SM-singlet fermions. The fermions remain light and, if ω is smaller than the confinement scale ΛQCDB,C ≡ Λ of SU(3)B,C , they efficiently break the hidden QCD strings and form light hadrons This is the region of parameters we are interested in: a TT model with light singlet cousin fermions, which for brevity we call TT in this work. As described, this setup successfully stabilizes the Higgs mass against the multi-TeV scale M. After rotating to the fermion mass eigenst√ate basis, the top Yukawa interactions couple the light eigenstate to the Higgs boson as (yt/ 2) sin θL cos θR h ψBψB. We concentrate on the less model-dependent production of hidden hadrons from decays of SM particles
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