Heavy-quark spin-symmetry partners of Z_b(10610) and Z_b(10650) molecules

¹ Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum, Germany
² Institute for Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow, Russia
³ Forschungszentrum Jülich, Institute for Advance Simulation, Institut für Kernphysik and Jülich Center for Hadron Physics, D-52425 Jülich, Germany
⁴ National Research Nuclear University MEPhI, 115409, Kashirskoe highway 31, Moscow, Russia
⁵ Moscow Institute of Physics and Technology, 141700, Institutsky lane 9, Dolgoprudny, Moscow Region, Russia

^* e-mail: vadimb@tp2.rub.de
^** e-mail: evgeny.epelbaum@ruhr-uni-bochum.de
^*** e-mail: arseniy.filin@ruhr-uni-bochum.de
^**** e-mail: c.hanhart@fz-juelich.de
^† ye-mail: nefediev@itep.ru

Published online: 18 October 2019

Abstract

Heavy-quark spin-symmetry (HQSS) partners of the isovector bottomonium like states Z_b(10610) and Z_b(10650) are predicted within the molecular picture. Treating both Z_b’s as shallow bound states, we solve the system of coupled-channel integral equations for the contact plus one-pion exchange (OPE) potentials to predict the location of the partner states with the quantum numbers J⁺⁺ (J = 0,1,2). In particular, we predict the existence of a narrow tensor 2⁺⁺ state residing a few MeV below the B^∗ B¯^∗ threshold. It is emphasised that the tensor part of the OPE potential in combination with HQSS breaking due to the nonvanishing B^∗ -B mass splitting has a significant impact on the location of this partner state.