Predictions of \begin{document}${\Upsilon{(4S) }\to {h_b(1P,2P) \pi^+\pi^-}}$\end{document} transitions

We study the contributions of intermediate bottomonium-like \begin{document}$Z_b$\end{document} states and the bottom meson loops in the heavy quark spin flip transitions \begin{document}$\Upsilon(4S) \to h_b(1P,2P) \pi^+\pi^-$\end{document} . Depending on the constructive or destructive interferences between the \begin{document}$Z_b$\end{document} -exchange and the bottom meson loops mechanisms, we predict two possible branching ratios for each process: BR \begin{document}$_{\Upsilon(4S) \to h_b(1P)\pi^+\pi^-}\simeq\big(1.2^{+0.8}_{-0.4}\times10^{-6}\big)$\end{document} or \begin{document}$\big( 0.5^{+0.5}_{-0.2}\times10^{-6}\big)$\end{document} , and \begin{document}$ {{BR}}_{\Upsilon(4S) \to h_b(2P)\pi^+\pi^-}\simeq \big(7.1^{+1.7}_{-1.1}\times10^{-10}\big)$\end{document} or \begin{document}$\big( 2.4^{+0.2}_{-0.1}\times10^{-10}\big)$\end{document} . The contribution of the bottom meson loops is found to be considerably larger than that of the \begin{document}$Z_b$\end{document} -exchange in the \begin{document}$\Upsilon(4S) \to h_b(1P) \pi\pi$\end{document} transitions, while its decay rates are not comparable to those of heavy quark spin conserved \begin{document}$\Upsilon(4S) \to \Upsilon(1S,2S) \pi\pi$\end{document} processes. We also predict the contribution of the charm meson loops in the branch fractions of \begin{document}$\psi(3S,4S) \to h_c(1P)\pi\pi$\end{document} .