Dispersive determination of the fourth generation lepton masses
Year: 2024
Type: article
Abstract: We continue our previous determination of the masses of the sequential fourth generation quarks in an extension of the Standard Model, and predict the mass m 4 ( m L ) of the fourth generation neutrino ν 4 (charged lepton L ) by solving the dispersion relations associated with heavy fermion decays. The results m 4 ≈ 170 GeV and m L ≈ 270 GeV are extracted from the dispersive analyses of the t → de + ν 4 and L − → ν 1 t ¯ d decay widths, respectively, where t ( d , e + , ν 1 ) denotes a top quark (down quark, positron, light neutrino). The predictions are cross-checked by examining the L − → ν 4 u ¯ d decay, u ¯ being an anti-up quark. It is shown that the fourth generation leptons with the above masses survive the current experimental bounds from Higgs boson decays into photon pairs and from the oblique parameters. We also revisit how the existence of the fourth generation leptons impacts the dispersive constraints on the neutrino masses and the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrix elements. It is found that the unitarity of the 3 × 3 PMNS matrix holds well up to corrections of O ( m ν 2 / m W 2 ) , m ν ( m W ) being a light neutrino (the W boson) mass, whose mixing angles and CP phase prefer the values θ 12 ≈ 34 ∘ , θ 23 ≈ 47 ∘ , θ 13 ≈ 5 ∘ and δ ≈ 200 ∘ in the normal-ordering scenario for neutrino masses.
Author: Hsiang-nan Li
Institutions: Institute of Physics, Academia Sinica, Academia Sinica
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,165
Award: G765356007
OpenAlex ID: W4405536406