Phenomenology of non-Abelian gauge and Goldstone bosons in a U(2) flavor model
Year: 2026
Type: article
Abstract: We investigate the phenomenological implications of the bosons associated with the S U ( 2 ) F subgroup in a simple and realistic U ( 2 ) F flavor model. While the Nambu-Goldstone boson of the U ( 1 ) F factor behaves as a standard QCD axion (an axiflavon) with suppressed flavor-violating couplings, the three degrees of freedom from S U ( 2 ) F have not been studied before. This work focuses on these states, considering both the case where S U ( 2 ) F is a global symmetry, yielding pseudo-Nambu-Goldstone bosons (PNGBs), and the case where it is a gauge symmetry with a potentially small coupling, yielding a triplet of (possibly) light gauge bosons. In both scenarios, these new bosons naturally feature unsuppressed flavor-violating couplings to Standard Model fermions in the mass basis. We derive the resulting predictions for flavor-changing neutral currents and lepton flavor violation, including exotic decays of mesons and leptons. Our analysis shows that processes like K → π X and μ → e X place the most stringent constraints, probing the flavor symmetry breaking scale v ϕ up to 10 11 – 10 12 GeV for light bosons, while heavier states are tested in B and τ decays, as well as by K − K ¯ mixing and μ → e γ . We demonstrate that low-energy flavor experiments provide a powerful probe of this framework, capable of testing ultrahigh symmetry breaking scales that surpass the limits set by astrophysical observations.
DOI: 10.1103/1mwt-bqsm
Authors: Lorenzo Calibbi, Jiangyi Yi
Institution: Nankai University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Awards: G5825055758, G7919756930
OpenAlex ID: W7154169344