Hyperfine splitting and the experimental candidates for ηb(2S)

Predictions for the hyperfine splitting of 2S bottomonia are compared with the two recent experimental candidates for the eta(b)(2S). The smaller splitting of the Belle state is consistent with unquenched lattice QCD computations, many potential models, and a model-independent relation which works well for charmonia. The larger splitting for the state extracted from CLEO data is inconsistent with most predictions. DOI: 10.1103/PhysRevD.87.034022