Assessment of $\Upsilon$-states above $B\overline{B}$-threshold using a constituent-quark-model based meson-meson coupled-channels framework

The $\Upsilon \left(10753\right)$ state has been recently observed by the Belle and Belle II collaborations with enough global significance to motivate an assessment of the high-energy spectrum usually predicted by any reasonable naïve quark model. In the framework of a constituent quark model which satisfactorily describes a wide range of properties of conventional hadrons containing heavy quarks, the quark-antiquark and meson-meson degrees of freedom have been incorporated with the goal of elucidating the influence of open-bottom meson-meson thresholds into the $\Upsilon$ states whose masses are within the energy range of the $\Upsilon \left(10753\right)$'s mass. It is well known that such effects could be relevant enough as to dynamically generate new states and thus provide a plausible explanation of the nature of the $\Upsilon \left(10753\right)$ state. In particular, we have performed a coupled-channels calculation in which the bare states $\Upsilon \left(4S\right)$, $\Upsilon \left(3D\right)$, $\Upsilon \left(5S\right)$, and $\Upsilon \left(4D\right)$ are considered together with the threshold channels $B\overline{B}$, $B{\overline{B}}^{*}$, $B^{*}{\overline{B}}^{*}$, $B_s{\overline{B}}_s$, $B_s{\overline{B}}_s^{*}$, and $B_s^{*}{\overline{B}}_s^{*}$. Among the results we have described, the following are of particular interest: (i) a richer complex spectrum is gained when thresholds are present and bare bound states are sufficiently nonrelativistic; (ii) those poles obtained in the complex energy plane do not have to appear as simple peaks in the relevant cross sections; and (iii) the $\Upsilon \left(10753\right)$ candidate is interpreted as a dressed hadronic resonance whose structure is an equally mixture of a conventional $b\overline{b}$ state and $B^{*}{\overline{B}}^{*}$ molecule.