Abstract
Using a data sample of events collected with the BESIII detector, we present a first observation of , and we measure its branching fraction to be . In contrast to the earlier discovery of a threshold enhancement in the -mass spectrum of the channel , denoted as , we do not find a similar enhancement in . An upper limit of at the 90% confidence level on the branching fraction of is obtained.
- Received 26 February 2019
DOI:https://doi.org/10.1103/PhysRevD.99.112010
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Published by the American Physical Society