Observation of Υ(2S) → ηΥ(1S) and search for related transitions
نویسندگان
چکیده
We report the first observation of Υ(2S) → ηΥ(1S), with branching fraction B = (2.1 −0.6 (stat.)± 0.3 (syst.))×10−4 and statistical significance 5.3σ. Data were acquired with the CLEO III detector at the CESR e+e− symmetric collider. This is the first process observed involving a b-quark spin flip. For related transitions, 90% confidence limits in units of 10−4 are B[Υ(2S) → π0Υ(1S)] < 1.8, B[Υ(3S) → ηΥ(1S)] < 1.8, B[Υ(3S) → π0Υ(1S)] < 0.7, and B[Υ(3S) → π0Υ(2S)] < 5.1.
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