A Measurement of the B{sup 0} {yields} J{psi}{pi}{sup +}{pi}{sup -} Branching Fraction

The authors present a preliminary measurement of the branching fraction for the decay of the neutral B meson into the final state J/{psi}{pi}{sup +}{pi}{sup -}. The data set contains approximately 56 million B{bar B} pairs produced at the {Upsilon}(4S) resonance and recorded by the BABAR detector at the PEP-II e{sup +}e{sup -} collider. The result of this analysis is {Beta}(B{sup 0} {yields} J/{psi}{pi}{sup +}{pi}{sup -}) = (5.0 {+-} 0.7 {+-} 0.6) x 10{sup -5}, where the first error is statistical and the second is systematic.