Study of B→X(3872)K, with X(3872)→J/ψπ+π−

Abstract

We present measurements of the decays B + → X ( 3872 ) K + and B 0 → X ( 3872 ) K 0 with X ( 3872 ) → J / ψ π + π − . The data sample used, collected with the BABAR detector at the PEP-II e + e − asymmetric-energy storage ring, corresponds to 455 × 10 6 B ¯¯¯ B pairs. Branching fraction measurements of B ( B + → X ( 3872 ) K + ) × B ( X ( 3872 ) → J / ψ π + π − ) = ( 8.4 ± 1.5 ± 0.7 ) × 10 − 6 and B ( B 0 → X ( 3872 ) K 0 ) × B ( X ( 3872 ) → J / ψ π + π − ) = ( 3.5 ± 1.9 ± 0.4 ) × 10 − 6 are obtained. We set an upper limit on the natural width of the X ( 3872 ) of Γ < 3.3 MeV / c 2 at the 90% confidence level.