Color-singlet J/psi production at alpha_s^6 in Upsilon decay

TL;DR

This paper calculates higher-order color-singlet contributions to Upsilon decay into J/psi, finding that these contributions increase the predicted branching ratio but still fall short of experimental measurements, highlighting the need for further investigation.

Contribution

It provides the first detailed calculation of alpha_s^6 order color-singlet contributions to Upsilon decay into J/psi, improving theoretical predictions.

Findings

The alpha_s^6 contributions increase the branching ratio prediction.

The predicted ratio R_cc is significantly larger than color-octet models.

The total predicted direct J/psi production rate remains below experimental values.

Abstract

To clarify the conflict between the theoretical predictions and experimental measurements of the inclusive J/psi production in Upsilon decay, We consider the alpha_s^6 order color-singlet contributions of processes Upsilon --> J/psi+gg and Upsilon --> J/psi+gggg. Both the branching ratio and J/psi momentum spectrum are calculated, and the branching ratio 4.7 x 10^{-4} is larger than the leading-order contribution (alpha_s^5, Upsilon --> J/psi+c\bar{c}g). Together with the QCD and QED leading-order contributions considered in our previous work, the color-singlet prediction of the branching ratio for the direct J/psi production is Br(Upsilon--> J/psi_{direct}+X)=0.90^{+0.49}_{-0.31} x 10^{-4}, which is still about 3.8 times less than the CLEO measurement. We also obtain a preliminary color-singlet prediction of R_{cc}=sigma(Upsilon --> J/psi+c\bar{c}+X)/ sigma(Upsilon --> J/psi+X) and find the value 0.39^{+0.21}_{-0.20} is much larger than the color-octet predictions, and suggest to measure this quality in future experimental analysis.