Properties of

The experimental line shapes available in the B$ \bar {B} $*, B*$ \bar {B} $*, hb(1P)π and hb(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 Zb(10610) and Zb(10650) are extracted for the best fits corresponding to χ2/d.o.f. of the order of one