Search for a dark vector gauge boson decaying to $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ using $\hat{I}\cdot \to \ddot{I}{€}^{+}\ddot{I}{€}^{-}{\hat{I}}^3$ decays

Abstract

We report a search for a dark vector gauge boson $U^{\prime }$ that couples to quarks in the decay chain $D^{\ast +}\to D^0\ddot{I}{€}^{+},D^0\to K_S^0\hat{I}\cdot ,\hat{I}\cdot \to U^{\prime }{\hat{I}}^3$, $U^{\prime }\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}$. No signal is found and we set a mass-dependent limit on the baryonic fine structure constant of $10^{-3}-10^{-2}$ in the $U^{\prime }$ mass range of 290 to 520 MeV/$c^2$. This analysis is based on a data sample of 976 fb${}^{-1}$ collected by the Belle experiment at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider.

6 pages, 4 figures