Observation of the Upsilon(1³D_J) Bottomonium State through Decays to π^+π^-Upsilon(1S)

Based on $122\times 10^6$ \ThreeS events collected with the \babar\ detector, we have observed the \OneDJ bottomonium state through the $\ThreeS\to\g\g\OneDJ\to\g\g\pip\pim\OneS$ decay chain.The significance for the $J=2$ member of the \OneDJ triplet is 5.8 standard deviations including systematic uncertainties.The mass of the $J=2$ state is determined to be $10164.5\pm0.8\,\rm{(stat.)}\pm0.5\,\rm{(syst.)}$~\mevcc.We use the $\pip\pim$ invariant mass distribution to confirm the consistency of the observed state with the orbital angular momentum assignment of the \OneDJ.