CLEO 1105 Branching fractions for Υ ( 3 S ) → π 0 h b and ψ ( 2 S ) → π 0 h c

Using e+e− collision data corresponding to 5.88 × 106 Υ(3S) [25.9 × 106 ψ(2S)] decays and acquired by the CLEO III [CLEO-c] detectors operating at the Cornell Electron Storage Ring, we study the single-pion transitions from Υ(3S) [ψ(2S)] to the respective spin-singlet states hb[c]. Utilizing only the momentum of suitably selected transition-π0 candidates, we obtain the upper limit B(Υ(3S) → πhb) < 1.2 × 10−3 at 90% confidence level, and measure B(ψ(2S) → πhc) = (9.0± 1.5± 1.3)× 10−4. Signal sensitivities are enhanced by excluding very asymmetric π0 → γγ candidates. ∗ Now at: Pacific Northwest National Laboratory, Richland, WA 99352