$Υ(6S)$ and triangle singularity in $e^+e^- \to B_1(5721) \bar B \to Z_b(10610) \, π$

We discuss the possibility that production of final states with bottomonium and light mesons at the peak $Υ(6S)$ in the $e^+e^-$ annihilation at approximately 11.00 GeV is in fact due to a triangular singularity at the threshold of the heavy meson pair production $B_1(5721) \bar B + c.c.$ through the process $e^+e^- \to B_1(5721) \bar B \to Z_b(10610) \, π$. The presence of the hidden-bottom resonance $Z_b(10610)$ then explains the observed enhanced production of the final channels with both ortho- and para- bottomonium states, $Υ(nS) ππ$ and $h_b(kP) ππ$. The discussed mechanism also predicts a distinct pattern for production of hidden-bottom states at the $Υ(6S)$ energy that can be tested by experiment.

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