Search for the Decays B^0 -> D^{(*)+} D^{(*)-}

TL;DR

This paper reports on a search for specific B^0 meson decay modes into D mesons using CLEO-II data, setting upper limits on their branching fractions due to limited observed signals.

Contribution

First search for these Cabibbo-suppressed B^0 decays with new upper limits on their branching fractions.

Findings

Observed one candidate for B^0 -> D^{*+} D^{*-} with a branching fraction estimate.

Set upper limits on B^0 -> D^{* extpm} D^ extmp{ } and B^0 -> D^+ D^- decays.

No significant signals found for the other decay modes.

Abstract

Using the CLEO-II data set we have searched for the Cabibbo-suppressed decays B^0 -> D^{(*)+} D^{(*)-}. For the decay B^0 -> D^{*+} D^{*-}, we observe one candidate signal event, with an expected background of 0.022 +/- 0.011 events. This yield corresponds to a branching fraction of Br(B^0 -> D^{*+} D^{*-}) = (5.3^{+7.1}_{-3.7}(stat) +/- 1.0(syst)) x 10^{-4} and an upper limit of Br(B^0 -> D^{*+} D^{*-}) < 2.2 x 10^{-3} at the 90% CL. For B^0 -> D^{*\pm} D^\mp and B^0 -> D^+ D^-, no significant excess of signal above the expected background level is seen, and we calculate the 90% CL upper limits on the branching fractions to be Br(B^0 -> D^{*\pm} D^\mp) < 1.8 x 10^{-3} and Br(B^0 -> D^+ D^-) < 1.2 x 10^{-3}.