Light Quark Spin Symmetry in $Z_b$ Resonances?

TL;DR

The paper suggests that recent Belle data indicates a suppressed light quark spin interaction in $Z_b$ resonances, implying potential new resonances due to light quark spin symmetry combined with heavy quark spin symmetry.

Contribution

It proposes that the light quark spin interaction in heavy meson pairs is weaker than expected, leading to predictions of additional resonances based on symmetry considerations.

Findings

Light quark spin interaction is strongly suppressed.

No activity observed at the $Z_b(10650)$ resonance mass.

Potential existence of four additional $I^G=1^-$ resonances.

Abstract

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.