Axion and neutrino physics in a U(1)-enhanced supersymmetric model
AbstractMotivated by the flavored Peccei-Quinn symmetry for unifying the flavor physics and string theory, we construct an explicit model by introducing a U(1) symmetry such that the U(1)X-[gravity]2 anomaly-free condition together with the standard model flavor structure demands additional sterile neutrinos as well as no axionic domain-wall problem. Such additional sterile neutrinos play the role of realizing baryogenesis via a new Affleck-Dine leptogenesis. We provide grounds for interpreting the U(1)X symmetry as a fundamental symmetry of nature. The model will resolve rather recent but fast-growing issues in astroparticle physics, including leptonic mixings and CP violation in neutrino oscillation, high-energy neutrinos, QCD axions, and axion cooling of stars. The QCD axion decay constant, through its connection to the astrophysical constraints of stellar evolution and the SM fermion masses, is shown to be fixed at FA=1.30-0.54+0.66×109 GeV (consequently, its mass is ma=4.34-1.49+3.37 meV and the axion-photon coupling is |gaγγ|=1.30-0.45+1.01×10-12 GeV-1). Interestingly enough, we show that neutrino oscillations at low energies could be connected to astronomical-scale baseline neutrino oscillations. The model predicts the nonobservational neutrinoless double beta (0νββ) decay rate as well as a remarkable pattern between the leptonic Dirac CP phase (δCP) and the atmospheric mixing angle (θ23); e.g., δCP≃220°–240°, 120°–140° for θ23=42.3° for normal mass ordering, and δCP≃283°, 250°, 100°, 70° for θ23=49.5° for the inverted one. We stress that future measurements on the θ23, 0νββ decay rate, the sum of active neutrino masses, the track-to-shower ratio of a cosmic neutrino, astrophysical constraints on axions, QCD axion mass, and the axion-photon coupling are of importance to test the model in the near future.