Properties of Z_b(10610) and Z_b(10650) from an analysis of experimental line shapes

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, D44780 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: vadimb@tp2.rub.de

Published online: 13 March 2019

Abstract

The experimental line shapes available in the B$\overline{B}$^*, B^*$\overline{B}$^*, h_b(1P)π and h_b(2P)π channels are analysed using a theoretical EFT-based framework manifestly consistent with unitarity and analyticity. The line shapes are calculated using a system of coupled channel integral equations with the potential consisting of the one-pion and one-eta meson exchange interactions from the lightest Goldstone boson octet as well as of several contact terms at leading and subleading orders which are adjusted to minimise the overall chi squared. The pole positions of the Z_b(10610) and Z_b(10650) are extracted for the best fits corresponding to χ²/d.o.f. of the order of one.