First observation of a Υ(1D) state -: art. no. 032001

We present the first evidence for the production of Y(1D) states in the four-photon cascade, Y(3S)-->gammachi(b)(2P), chi(b)(2P)-->gammaY(1D), Y(1D)-->gammachi(b)(1P), chi(b)(1P)-->gammaY(1S), followed by the Y(1S) annihilation into e(+)e(-) or mu(+)mu(-). The signal has a significance of 10.2 standard deviations. The measured product branching ratio for these five decays, (2.5+/-0.5+/-0.5)x10(-5), is consistent with the theoretical estimates. The data are dominated by the production of one Y(1D) state consistent with the J=2 assignment. Its mass is determined to be (10161.1+/-0.6+/-1.6) MeV, which is consistent with the predictions from potential models and lattice QCD calculations. We also searched for Y(3S)-->gammachi(b)(2P), chi(b)(2P)-->gammaY(1D), followed by either Y(1D)-->etaY(1S) or Y(1D)-->pi(+)pi(-)Y(1S). We find no evidence for such decays and set upper limits on the product branching ratios.