Light Quark Spin Symmetry in $Z_b$ Resonances?

Understand

It is argued that the recent Belle data, consistent with no activity in the spectrum of the $B^* \bar B + B \bar B^*$ pairs at the mass of the $Z_b(10650)$ resonance, imply that the part of the interaction between heavy mesons that depends on the total spin of the light quark and antiquark is strongly suppressed.

• In particular this part appears to be significantly weaker than can be inferred from pion exchange.
• If confirmed by future more detailed data, the symmetry with respect to the light quark spins, in combination with the heavy quark spin symmetry, would imply existence of four additional $I^G=1^-$ resonances at the thresholds for heavy meson-antimeson pairs.