Minimal extension of the Standard Model with a mirror symmetry between fundamental fermions and a possible origin of dark matter

Abstract

In this paper, we propose a specific, nontrivial extension of the Standard Model of weak interactions based on the ${SU(2)}_L\times{U(1)}_Y\times{U(1)}_C$ group. Our motivation follows from the identification of the globally conserved charge $\Omega=\mathrm{B}-\mathrm{L}-\mathrm{Q}$ as a neutrino charge. An intriguing feature of the model is the emergence of a mirror symmetry between neutrinos and electrically charged leptons, as well as between up and down quarks. Following the spontaneous breaking of the weak gauge symmetry with the use of the Goldstone-Higgs iso-doublet, all elementary fermions acquire Dirac masses from Yukawa interaction. The $W^\pm$ and $Z$ bosons also acquire masses, although with a modified relationship between their respective masses, as compared to the Standard Model. Our model accounts for both chiral components of the neutrino and offers an explanation for the non-observability of the right-chiral neutrino. Additionally, it forbids neutrinoless double-beta decay. Spontaneous breaking of the local $U(1)$ symmetry leads to the new gauge boson $ \mathit{\Omega}_\mu$ mass $M_\mathit{\Omega}$, which we assume to be greater than the mass $m_\chi$ of a new scalar, Higgs-like field $\chi$. The cosmological stability of $\chi$, predicted under this condition, allows for its interpretation as dark matter, interacting exclusively with $\mathit{\Omega}_\mu$ and gravity. From this perspective, we solve and analyze a system of Boltzmann equations that describe the thermal evolution of the number density of $\chi$ dark matter and the $\mathit{\Omega}_\mu$ mediator field within the context of the $\mathrm{\Lambda CDM}$ cosmological model. Specifically, we estimate the coupling constant $q$ to be in the range of $\sim 10^{-8.5}\ g$ to $\sim 10^{-6}\ g$ which ensures cosmological stability of the $\chi$ particles.