Search for exclusive B decays to J and η or π0 with the L3 detector

A search for exclusive decays of Bd0 and Bs0 mesons has been performed in the channels Bd0 → Jη, Bs0 → Jη, Bd0 → Jπ0 and Bs0 → Jπ0. The data sample consisted of more than three and half million hadrozic Z decays collected by the L3 experiment at LEP from 1991 through 1995. No candidate events have been observed for any of the modes thus determining upper limits at 90% confidence level: 3.2 × 10−4 on Br(Bd0 → Jπ0) and the first experimental limits: Br(Bd0 → Jη) < 1.2 × 10−3, Br(Bs0 → Jη) < 3.8 × 10−3, Br(Bs0 → Jπ0) < 1.2 × 10−3.