The nature of the scalar field responsible for the cosmological inflation is found to be rooted in the most fundamental concept of the Weyl’s differential geometry: the parallel displacement of vectors in curved spacetime. Within this novel geometrical scenario, the standard electroweak theory of leptons based on the SU(2)L⊗U(1)Y as well as on the conformal groups of spacetime Weyl’s transformations is analyzed within the framework of a general-relativistic, conformally-covariant scalar–tensor theory that includes the electromagnetic and the Yang–Mills fields. A Higgs mechanism within a spontaneous symmetry breaking process is identified and this offers formal connections between some relevant properties of the elementary particles and the dark energy content of the Universe. An “effective cosmological potential”: Veff is expressed in terms of the dark energy potential: |VΛ| via the “mass reduction parameter”: |ζ|≡√|Veff||VΛ|, a general property of the Universe. The mass of the Higgs boson, which is considered a “free parameter” by the standard electroweak theory, by our theory is found to be proportional to the mass MU≡√|Veff| which contributes to the measured Cosmological Constant, i.e. the measured content of vacuum-energy in the Universe. The nonintegrable application of the Weyl’s geometry leads to a Proca equation accounting for the dynamics of a ϕρ-particle, a vector-meson proposed as an optimum candidate for Dark Matter. The peculiar mathematical structure of Veff offers a clue towards a very general resolution in 4-D of a most intriguing puzzle of modern quantum field theory, the “cosmological constant paradox”(here referred to as: “Λ-paradox”). Indeed, our “universal” theory offers a resolution of the “Λ-paradox” for all exponential inflationary potentials: VΛ(ϕ)∝e−nϕ, and for all linear superpositions of these potentials, where n belongs to the mathematical set of the “real numbers”. An explicit solution of the Λ-Paradox is reported for n=2. The results of the theory are analyzed in the framework of the recent experimental data of the PLANCK Mission. The average vacuum-energy density in the Universe is found: ρvac=(3.44×10−3)4(eV)4, the mass-reduction parameter: |ζ|≈10−38 and the value of the “cosmological constant”: Λ=3,86×10−64(eV/c2)2. A quite remarkable result of the theory consists of the complete formulation of the Einstein equation including in its structure the “cosmological constant”, Λ. This was the term that Einstein added “by hand” to his famous equation. The critical stability of the Universe is also discussed.