Observation of the decay
Abstract
Using 14 million (2S) events collected with the BESII detector, branching fractions of and are determined to be: ()=(2.9+1.3-1.70.4)× 10-5 and ()=(13.3+2.4-2.71.9)× 10-5. The results confirm the violation of the "12%" rule for these two decay channels with higher precision. A large isospin violation between the charged and neutral modes is observed.
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