Observation of ThreePStates in the Radiative Decay ofϒ(2S)

Abstract

The inclusive photon spectrum in hadronic decays of the $\Upsilon \mathrm{}\left(2S\right)\mathrm{}$ is measured with the Crystal Ball detector at DORIS II. Four well separated photon lines, which are consistent with the decay hypothesis $\Upsilon \mathrm{}\left(2S\right)\mathrm{}\to \gamma +{}_{}{}^3{}_{}{}^{}P_{2,1,0}^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}P_{2,1}^{}{}_{}{}^{}\to \gamma \Upsilon \mathrm{}\left(1S\right)\mathrm{}$, are observed. The energies of the lines from the primary transitions are $E_{\gamma 1}=110.4\mathrm{}\pm 0.8\pm 2.2$ MeV, $E_{\gamma 2}=130.6\mathrm{}\pm 0.8\pm 2.4$ MeV, and $E_{\gamma 3}=163.8\mathrm{}\pm 1.6\pm 2.7$ MeV; the branching fractions are (5.8±0.7±1.0)%, (6.5±0.7±1.2)%, and (3.6±0.8±0.9)%, respectively. The secondary transitions center at $〈E_{\gamma }〉\simeq 430$ MeV with a combined branching fraction of (3.6±0.7±0.5)%.