Exotic molecular states in the decays of vector bottomonia

¹ Helmholtz-Institut für Strahlen-und Kernphysik and Bethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn, Germany
² Institute for Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow, Russia
³ P.N. Lebedev Physical Institute of the Russian Academy of Sciences, 119991, Leninskiy Prospect 53, Moscow, Russia
⁴ Ruhr University Bochum, Faculty of Physics and Astronomy, Institute for Theoretical Physics II, D-44780 Bochum, Germany
⁵ Forschungszentrum Jülich, Institute for Advanced Simulation, Institut für Kernphysik and Jülich Center for Hadron Physics, D-52425 Jülich, Germany
⁶ National Research Nuclear University MEPhI, 115409, Kashirskoe highway 31, Moscow, Russia

^* e-mail: nefediev@lebedev.ru

Published online: 17 June 2019

Abstract

The most recent experimental data for the decays of the vector bottomonium γ(10860) proceeding through the formation of the states Z_b(10610) and Z_b(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 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 Z_b’s are determined as a prediction. In particular, both Z_b states are found to be described by resonance poles located on the unphysical Riemann sheets in the vicinity of the corresponding thresholds. The heavy quark spin symmetry (HQSS) is employed to predict, in a parameter-free way, the pole positions and the line shapes in the elastic and inelastic channels for the Z_bs’ 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 vector bottomonium Υ(10860) and are expected to be detected in the Belle-II experiment.