Search for Charmonium(-like) states decaying into the $\hat{I}{\text{c◯}}^{-}\bar{\hat{I}}{\text{c◯}}^{+}$ final states

Abstract

Recently, the BESIII experiment performed a measurement of the energy-dependent Born cross section and the effective form factor for the $e^{+}{e}^{-}\to \hat{I}{\text{c◯}}^{-}\bar{\hat{I}}{\text{c◯}}^{+}$ reaction at center-of-mass energies ranging from 3.4 to 4.7 GeV. A fit to the energy dependence of the dressed cross section is performed. With the assumption of a charmonium (like) resonance [i.e., $\ddot{I}ˆ(3770)$, $\ddot{I}ˆ(4040)$, $\ddot{I}ˆ(4160)$, $Y(4230)$, $Y(4360)$, $\ddot{I}ˆ(4415)$, or $Y(4660)$] plus a power-law function, the fit is applied to the data from the recent BESIII measurement, which was additionally combined with previous CLEO-c measurement data. No significance is found. The products of the branching fraction and the two electronic partial widths for the assumed charmonium(-like) states decaying into the $\hat{I}{\text{c◯}}^{-}\bar{\hat{I}}{\text{c◯}}^{+}$ final states are also provided. In addition, by taking the world average values of the electronic branching fraction, the branching fractions for $\ddot{I}ˆ(3770)$, $\ddot{I}ˆ(4040)$, $\ddot{I}ˆ(4160)$, $\ddot{I}ˆ(4415)$ decaying into $\hat{I}{\text{c◯}}^{-}\bar{\hat{I}}{\text{c◯}}^{+}$ final states at the 90\% confidence level are determined for the first time. These are found to be at least an order of magnitude larger than expected from predictions using a scaling based on the observed electronic widths.

8 pages, 4 figures, Consistent with the publication in Nuclear Physics B 2026, 1025, 117388

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