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

Abstract

A light boson U from an extra U (1) interpolates between a generalized dark photon coupled to Q, B and Li (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, withacting in a dark sector and F ′ on possible semi-inert 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 QU of chiral quarks and leptons is a combination of Q, B, Li and T3L with the axial FA. 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 gA, usually restricted to < ∼ 2 × 10 −7 mU (MeV), lead to effective pseudoscalar ones gP = gA × 2m q,l /mU = 2 1/4 G 1/2 F m q,l A± . A± is proportional to an invisibility parameter r = cos θA 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 ≃ 2 × 10 −6 mU (MeV) r/sin 2β . We discuss phenomenological implications for meson decays, neutrino interactions, atomic-physics parity violation, naturally suppressed π 0 → γ U decays, etc.. The U boson fits within the grand-unification framework, in symbiosis with a SU (4)es electrostrong symmetry broken at the GUT scale, with QU depending on Q, B −L, FA and T3A through three parameters γY , γA and η .

A stringy model of pointlike particles

“…It is shown in [13] that PBH DM can be produced only in two limited ranges of 10 −15 or 10 −12 Solar masses (2 × 10 30 kg). Dark photons open a rich phenomenology described [14].…”

The X17 boson and the $^3$H$(p,e^+ e^-)^4$He and $^3$He$(n,e^+ e^-)^4$He processes: a theoretical analysis

“…The observation of the 8 Be and 4 He anomalies has triggered a rapidly growing number of theoretical studies [19][20][21][22][23][24][25][26][27][28], see Ref. [29] for a critical review.…”