Line shapes in \Upsilon(5S) \to B^{(*)} \bar{B}^{(*)}\pi with Z(10610) and Z(10650) using effective field theory

Understand

The Belle collaboration recently discovered two resonances, $Z_b(10610)$ and $Z_b(10650)$ --- denoted $Z_b$ and $Z_b^\prime$ --- in the decays $\Upsilon(5S) \to \Upsilon(nS) \pi^+ \pi^-$ for $n$ = 1, 2, or 3, and $\Upsilon(5S) \to h_b(mP) \pi^+ \pi^-$ for $m = 1$ or 2.

• These resonances lie very close to the $B^* \bar{B}$ and $B^* \bar{B}^*$ thresholds, respectively.
• A recent Belle analysis of the three-body decays $\Upsilon(5S) \to [B^{(*)} \bar{B}^{(*)}]^{\mp} \pi^\pm$ gives further evidence for the existence of these states.
• In this paper we analyze this decay using an effective theory of $B$ mesons interacting via strong short-range interactions.