Speaker
Dr
Alexey Nefediev
(Lebedev Physical Institute)
Description
The most recent experimental data for the decays of the vector bottomonium Upsilon(10860) proceeding through the formation of the states Zb(10610) and Zb(10650) are analysed simultaneously using solutions of the Lippmann-Schwinger equations which respect constraints from unitarity and analyticity. The interaction potential in the open-bottom channels B(*)-anti-B* contains short-range interactions as well as the one-pion exchange; both types of the interaction are taken into account fully nonperturbatively. This way, all parameters of the interaction are fixed directly from the data and the pole positions for the Zb's are determined as a prediction. In particular, both Zb states are found to be described by poles located on the unphysical Riemann sheets in the vicinity of the corresponding thresholds: the Zb(10610) is associated with a virtual state residing just below the B-anti-B* threshold while the Zb(10650) state is most likely located just above the B*-anti-B* threshold. The heavy quark spin symmetry is employed to predict, in a parameter-free way, the pole positions and the line shapes in the elastic and inelastic channels for the Zbs' spin partner states W_bJ with the quantum numbers J++ (J=0,1,2). Such spin partners can be produced in radiative decays of the Upsilon(10860) state and, if they exist, are expected to be detected in the Belle-II experiment.
Primary author
Dr
Alexey Nefediev
(Lebedev Physical Institute)
