Insights Into Z(B)(10610) And Z(B)(10650) From Dipion Transitions From Upsilon(10860)

The dipion transitions Upsilon(10860) -> pi(+) pi(-)Upsilon(nS) (n = 1, 2, 3) are studied in the framework of a unitary and analytic coupled-channel formalism previously developed for analyzing experimental data on the bottomoniumlike states Z(b) (10610) and Z(b )(10650) [Phys. Rev. D 98, 074023 (2018)] and predicting the properties of their spin partners [Phys. Rev. D 99, 094013 (2019)]. In this work we use a relatively simple but realistic version of this approach, where the scattering and production amplitudes are constructed employing only short-ranged interactions between the open- and hidden-flavor channels consistent with the constraints from heavy quark spin symmetry, for an extended analysis of the experimental line shapes. In particular, the transitions from the Upsilon(10860) to the final states pi pi h(b) (mP) (m = 1, 2) and pi B(*)(B) over bar* already studied before, are now augmented by the Upsilon(10860) -> pi(+)pi(-)Upsilon(nS) final states (n = 1, 2, 3). This is achieved by employing dispersion theory to account for the final state interaction of the pi pi subsystem including its coupling to the K (K) over bar channel. Fits to the two-dimensional Dalitz plots for the pi(+)pi(-)Upsilon final states were performed. Two real subtraction constants are adjusted to achieve the best description of the Dalitz plot for each Upsilon(nS) (n = 1, 2, 3) while all the parameters related to the properties of the Z(b)s are kept fixed from the previous study. A good overall description of the data for all Upsilon(10860) -> pi(+)pi(-) Upsilon(nS) channels achieved in this work provides additional strong support for the molecular interpretation of the Z(b) states.