Effect of $Z_b$ states on ${\rm Y}(3S)\to {\rm Y}(1S)\pi \pi$ decays

Yun-Hua Chen, Johanna T. Daub, Feng-Kun Guo +3

Within the framework of dispersion theory, we analyze the dipion transitions between the lightest ${\rm Y}$ states, ${\rm Y}(nS)\to {\rm Y}(mS)\pi \pi$ with $m<n\le 3$. In particular, we co…