Year: 2026
Type: article
Abstract: For fixed Standard Model (SM) non-Abelian representations of 15 chiral fermions with arbitrary hypercharges, anomaly cancellation admits the usual assignment and a distinct nonstandard solution. In the latter, the exotic quark and lepton weak doublets and exotic lepton singlet have zero hypercharge, whereas the two exotic quark singlets carry opposite hypercharges $-q$ and $q$. The neutral exotic lepton singlets naturally provide heavy neutrinos. With two copies, the minimal model realizes the minimal type-I seesaw, yielding one massless active neutrino, and predicts $m_{ββ}=1.2$--$4.1$ meV for normal ordering and $15.9$--$48.9$ meV for inverted ordering. In a direct SM realization, generating exotic-quark masses through the SM Higgs mechanism fixes their electric charges to $\pm 1/2$. A separate $SU(2)_{L'}$ realization of the nonstandard solution can allow exotic-quark masses ranging from several TeV to 10 TeV with order-one Yukawa couplings while all charged exotic particles carry charges $\pm q$. In both cases, the lightest exotic quark and lepton are generically stable, providing distinctive and potentially testable signatures while remaining compatible with current constraints.
DOI: 10.1103/gx3d-v5t7
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Award: G3289481219
OpenAlex ID: W7203627573