Inclusive decays of B-meson to J/ψ and χ _c1 using $\boldsymbol {386\times 10^{6} B\bar {B}}$ events

Abstract

The inclusive decays of B-mesons to charmonium have been studied in a data sample of 386 million $B\bar {B}$ events. The data sample has been collected by the Belle detector at the KEKB asymmetric energy e ⁺ e ⁻ collider operating at the Υ(4S) resonance. The branching fractions have been measured for the inclusive decays to J/ψ + X and χ _c1 + X. The measured branching fraction for J/ψ + X is $\mathcal {B}(B \to J/\psi (\to e^{+}e^{-})+X) = (1.10\pm 0.005\pm 0.057)\%$ and $\mathcal {B}(B\to J/\psi (\to \mu ^{+}\mu ^{-})+X) = (1.08\pm 0.004\pm 0.056)\%$, while the inclusive χ _c1 + X branching fraction is found to be $\mathcal {B}(B\to \chi _{c1}+X) = (0.44\pm 0.01\pm 0.06)\%$. The feed-down contribution from higher charmonium states is subtracted from the measured branching fractions and the direct branching fractions are obtained to be $\mathcal {B}(B\to J/\psi +X) = (0.77\pm 0.04\pm 0.06)\%$ and $\mathcal {B}(B \to \chi _{c1}+X) = (0.41\pm 0.01\pm 0.06)\%.$