Hyperfine splitting and the experimental candidates for \eta_b(2S)

TL;DR

This paper compares theoretical predictions of hyperfine splitting in 2S bottomonia with recent experimental data, highlighting discrepancies and consistencies among models and measurements.

Contribution

It evaluates the compatibility of experimental candidates for (2S) with various theoretical models and lattice QCD predictions.

Findings

Belle's (2S) splitting aligns with lattice QCD and potential models.

CLEO's (2S) splitting is inconsistent with most theoretical predictions.

Unquenched lattice QCD and model-independent relations support smaller hyperfine splitting.

Abstract

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.