Study of $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\rm Y}(1D)$ at Belle II

Abstract

The bottomonium spectrum, consisting of bound states of a $b$ quark and an anti-$b$ quark, provides an excellent laboratory for probing quantum chromodynamics in the non-perturbative regime. While S and P-wave bottomonium states are well studied experimentally, information on D-wave states remains scarce. We search for the D-wave bottomonium states ${{\rm Y}}_2(1D)$ and ${{\rm Y}}_3(1D)$ via the decay of a vector bottomonium-like state ${\rm Y}(10753)$ in the reaction $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\rm Y}(1D)$, using $19.6{\mathrm{fb}}^{-1}$ of data collected with the Belle II detector at center-of-mass energies $\sqrt{s}=10.653$, 10.701, 10.745, and 10.805~GeV, in the vicinity of the ${\rm Y}(10753)$ resonance. No significant signals are observed. We set upper limits at the 90\% credibility level on the products of the cross sections and branching fractions, $\sigma [e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{{\rm Y}}_2(1D)]\times \mathcal{B}[{{\rm Y}}_2(1D)\to \gamma {\chi }_{b1}]$ and $\sigma [e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{{\rm Y}}_3(1D)]\times \mathcal{B}[{{\rm Y}}_3(1D)\to \gamma {\chi }_{b2}]$, at each center-of-mass energy.

arXiv comment22 pages, 4 figures