Status and new results on the Zb resonances

TL;DR

This paper reviews the discovery and properties of charged bottomonium-like Zb states, including new experimental results supporting their molecular nature and isotriplet structure.

Contribution

It provides updated experimental findings on Zb states, including decay modes and isospin partners, reinforcing their interpretation as molecular bottomonium states.

Findings

Observation of Zb decays to B(*)B*

Evidence for neutral Zb member

Properties consistent with molecular interpretation

Abstract

Recently Belle observed two charged bottomonium-like states, Zb(10610) and Zb(10650), that are produced in the Upsilon(5S) -> Zb pi transitions and that decay to Upsilon(nS) pi (n=1,2,3) and h_b(mP) pi (m=1,2) channels. The masses of these states are close to the $B\bar{B}^*$ and $B^*\bar{B}^*$ thresholds, and their favored spin-parities are $J^P=1^+$. We review status and new results on the Zb states, that include the observation of the $Z_b\to B^{(*)}\bar{B}^*$ decays and an evidence for the neutral member of the Zb isotriplet. All properties of the Zb states are consistent with their molecular interpretation.