U boson interpolating between a generalized dark photon or dark Z, an axial boson, and an axionlike particle

A light boson U from an extra U(1) interpolates between a generalized dark photon coupled to Q, B, and L-i (or B - L), plus possibly dark matter, a dark Z coupled to the Z current, and one axially coupled to quarks and leptons. We identify the corresponding U(1)(F) symmetries, with F = gamma Y-Y + gamma B-B + gamma(Li) L-i + gamma F-A(A) + gamma F-F'' + gamma F-d(d), F-d acting in a dark sector and F' on possible semi-inert Brout-Englert-Higgs (BEH) doublets uncoupled to quarks and leptons. The U current is obtained from the U(1)(F) and Z currents, with a mixing determined by the spin-0 BEH fields. The charge Q(U) of chiral quarks and leptons is a combination of Q, B, L-i, and T-3L with the axial F-A. It involves in general isovector and isoscalar axial terms, in the presence of two BEH doublets. A longitudinal U with axial couplings has enhanced interactions and behaves much as an axionlike particle. Its axial couplings g(A), usually restricted to less than or similar to 2 x 10(-7) m(U)(MeV), lead to effective pseudoscalar ones g(P) = g(A) x 2m(q,l)/m(U) = 2(1/4)G(F)(1/2)m(q,l) A(+/-). A(+/-) is proportional to an invisibility parameter r = cos theta(A) induced by a singlet v.e.v., possibly large and allowing the U to be very weakly interacting. This allows for a very small gauge coupling, expressed with two doublets and a singlet as g '' = 4 similar or equal to 2 x 10(-6) m(U)(MeV) r/sin 2 beta. We discuss phenomenological implications for meson decays, neutrino interactions, atomic-physics parity violation, naturally suppressed pi(0) -> gamma(U) decays, etc. The U boson fits within the grand unification framework, in symbiosis with a SU(4)(es) electrostrong symmetry broken at the grand unification scale, with Q(U) depending on Q, B - L, F-A, and T-3A through three parameters gamma(Y), gamma(A), and eta.

Automated summary

The passage discusses a light boson U from an extra U(1) and its interactions with various particles and fields, including dark matter and Z bosons. It also explores the concept of U(1)(F) symmetries and the role of BEH doublets in determining the charge of chiral quarks and leptons. Additionally, it mentions the enhanced interactions of a longitudinal U with axial couplings and its potential coupling strengths based on certain parameters.