Although heavy-quark symmetry implies a $B_1\overline{B}$ molecular partner of the $D_1\overline{D}$ molecule, no such state has been observed experimentally to date. In this work, we propose that the experimentally observed $\mathrm{\Upsilon }(11020)$ may be a candidate for such a molecular state, although it may also contain a $B_1{\overline{B}}^{*}$ component. To explore whether the $\mathrm{\Upsilon }(11020)$ can be interpreted as an $S$-wave $B_1\overline{B}–B_1{\overline{B}}^{*}$ molecule, we calculate its strong decay widths within this molecular scenario using the compositeness condition and effective Lagrangians. The coupling of the $\mathrm{\Upsilon }(11020)$ to its constituents $B_1$ and ${\overline{B}}^{(*)}$ is determined by fitting the available experimental data on $\mathrm{\Upsilon }(11020)\to e^{+}{e}^{-}$ and $\mathrm{\Upsilon }(11020)\to {\chi }_{bJ}\pi \pi \pi$ decays. With the extracted coupling, we compute the partial decay widths of the $\mathrm{\Upsilon }(11020)$ into $B_{(s)}^{(*)}{\overline{B}}_{(s)}^{(*)}$, $\pi \pi \mathrm{\Upsilon }(nS)$, $\pi \pi h_b(nP)$, and $\pi \pi \pi {\chi }_{b1}$ via hadronic loops, as well as the three-body $B^{*}\pi {\overline{B}}^{(*)}$ decays via tree-level diagrams. Our results suggest that the $\mathrm{\Upsilon }(11020)$ can indeed be interpreted as an $S$-wave $B_1\overline{B}–B_1{\overline{B}}^{*}$ molecule with a dominant $B_1\overline{B}$ component, whose main decay channel is $B_s^{*}{\overline{B}}^{*}$. Moreover, the partial widths for $\mathrm{\Upsilon }(11020)\to \pi \pi \mathrm{\Upsilon }(nS)$ and $\mathrm{\Upsilon }(11020)\to \pi \pi h_b(nP)$ are found to be only a few eV. In contrast, the widths for $\mathrm{\Upsilon }(11020)\to \pi \pi \pi {\chi }_{bJ}$ are considerably larger, with $\pi \pi \pi {\chi }_{b1}$ reaching up to 0.167 MeV, while the yet-unobserved $\pi \pi \pi {\chi }_{b0}$ channel could be as large as 0.754 keV. These distinctive decay patterns could serve as experimental signatures of the molecular nature of the $\mathrm{\Upsilon }(11020)$, and their confirmation would provide a test of the applicability of heavy-quark symmetry.

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• Particle decays
• Particle interactions
• Particle phenomena