Higher-order QCD corrections to $\Upsilon$ decay into double charmonia

TL;DR

This paper calculates higher-order QCD corrections to $$ decays into double charmonia, improving theoretical predictions and matching experimental data, especially for the $ o J/+h_{c1}$ process.

Contribution

It provides the first next-to-leading order QCD calculations for $$ decays into double charmonia within the nonrelativistic QCD framework, reducing scale dependence and aligning with experimental results.

Findings

QCD corrections significantly reduce decay width scale dependence.

Branching fraction for $ o J/+h_{c1}$ matches Belle measurements.

Polarization of $J/$ is independent of nonperturbative parameters.

Abstract

In this work, we study the exclusive decay of $\Upsilon$ into $J/\psi$ in association with $\eta_c$ ($\chi_{c0,1,2}$). The decay widths for different helicity configurations are evaluated up to QCD next-to-leading order within the nonrelativistic QCD framework. We find that the QCD corrections notably mitigate the renormalization scale dependence of the decay widths for all the processes. The branching fraction of $\Upsilon\rightarrow J/\psi+\chi_{c1}$ is obtained as $3.73^{+5.10+0.10}_{-2.06-1.19}\times 10^{-6}$, which agrees well with the Belle measurement, i.e., ${\rm Br}(\Upsilon\rightarrow J/\psi+\chi_{c1})=(3.90\pm1.21\pm0.23)\times10^{-6}$. For the other processes, our results of the branching fractions are compatible with the upper limits given by the Belle experiments, except for $\Upsilon(2S)\to J/\psi +\chi_{c1}$, where some tension exists between theory and experiment. Having the polarized decay widths, we study the $J/\psi$ polarization, which turn out to be independent of any nonperturbative parameters. Further, according to our calculation, it is promising to measure all the processes at Super B factory thanks to the high luminosity.