Exclusive Measurements in B to D^* N Nbar X

Abstract

We report the first observation of exclusive decays of the type B to D^* N Nbar X, where N is a nucleon. Using a sample of 9.7 x 10^6 BBbar pairs collected with the CLEO detector operating at the Cornell Electron Storage Ring, we measure the branching fractions B(B^0 to D^*-p pbar pi^+) = (6.5+1.3-1.2 +-1.0) x 10^-4, and B(B^0 to D^*- p nbar) = (14.5+3.4-3.0 +-2.7) x 10^-4. The charge conjugate process is implied in the reconstruction of B^0 to D^*- p nbar, only the mode with the antineutron is used in our measurement because neutrons do not have a distinctive annihilation signature. Antineutrons are used for the first time in the exclusive reconstruction of a B meson. By finding conclusive evidence for the existence of decay modes of the type B to D N Nbar X, we challenge the assumption that the B to Baryons rate is dominated by decays to charmed mesons.