Chromopolarizabilities of bottomonia from the $Υ(2S,3S,4S) \to Υ(1S,2S)ππ$ transitions

Abstract

The dipion transitions $Υ(2S,3S,4S) \to Υ(1S,2S)ππ$ are systematically studied by considering the mechanisms of the hadronization of soft gluons, exchanging the bottomoniumlike $Z_b$ states, and the bottom-meson loops. The strong pion-pion final-state interaction, especially including the channel coupling to $K\bar{K}$ in the $S$-wave, is taken into account in a model-independent way using the dispersion theory. Through fitting to the available experimental data, we extract values of the transition chromopolarizabilities $|α_{Υ(mS)Υ(nS)}|$, which measure the chromoelectric couplings of the bottomonia with soft gluons. It is found that the $Z_b$ exchange has a slight impact on the extracted chromopolarizablity values, and the obtained $|α_{Υ(2S)Υ(1S)}|$ considering the $Z_b$ exchange is $(0.29\pm 0.20)~\text{GeV}^{-3}$. Our results could be useful in studying the interactions of bottomonium with light hadrons.