Sequential Decays of the Υ″

Abstract

We have studied the decay chain Υ″→${\mathrm{\chi }}_{\mathrm{b}}^{\prime }$(${\mathrm{\chi }}_{\mathrm{b}}$)γ→Υ′(Υ)γγ→μμ(ee)γγwith the CUSB II detector at the Cornell Electron Storage Ring. For a sample of 1.33×${10}^6$ Υ″'s we find ≈400 events. We measure branching ratios for${\mathrm{\chi }}_{\mathrm{bJ}}^{\prime }$→Υ′(Υ)γ and, using calculated E1 rates, we derive total and hadronic widths of the${\mathrm{\chi }}_{\mathrm{b}}^{\prime }$ states. From these widths we obtain values of ${\mathrm{a}}_{\mathrm{s}}$ in the range between 0.13 and 0.21, in agreement with other determinations. We observe the suppressed decay Υ″→${\mathrm{\chi }}_{\mathrm{b}}$γ. The measured branching ratio suggests that relativistic effects are important. We also determine the branching ratios for Υ″→Υ′${\mathrm{\pi }}^0$ ${\mathrm{\pi }}^0$ to be (1.3±0.4±0.2)% andΥ″→Υ${\mathrm{\pi }}^0$ ${\mathrm{\pi }}^0$ to be (1.8±0.3±0.2)%. © 1991 The American Phsyical Society