Search for the dark photon in , , , and decays at Belle

Park, S.-H.*; Tanida, Kiyoshi   ; Belle Collaboration*; 217 of others*

We present a search for the dark photon in the decays, where subsequently decays to , , and . The search is performed by analyzing events collected by the Belle detector at the KEKB energy-asymmetric collider at the resonance. No signal is found in the dark photon mass range , and we set upper limits of the branching fraction of at the 90% confidence level. The products of branching fractions, and , have limits of the order of depending on the mass. Furthermore, considering decay rate to each pair of charged particles, the upper limits of are of the order of -. From the upper limits of , we obtain the Higgs portal coupling for each assumed dark photon and dark Higgs mass. The Higgs portal couplings are of the order of - at and - at .