$\Upsilon$ decay to two-charm quark jets as a Probe of the Color Octet Mechanism

TL;DR

This paper calculates the decay rate of bottomonium to two charm jets, highlighting the dominance of the color-octet mechanism and its potential for experimental testing of QCD models.

Contribution

It provides a detailed calculation of the decay rate including both color-singlet and color-octet contributions at tree and one-loop levels, emphasizing the significance of the color-octet mechanism.

Findings

Color-octet contribution is much larger than color-singlet.

QCD corrections significantly affect the endpoint behavior of charm jets.

Experimental measurements can test the color octet mechanism.

Abstract

We calculate the decay rate of bottomonium to two-charm quark jets $\Upsilon \to c \bar c$ at the tree level and one-loop level including color-singlet and color-octet $b \bar b$ annihilations. We find that the short distance coefficient of the color-octet piece is much larger than the color-singlet piece, and that the QCD correction will change the endpoint behavior of the charm quark jet. The color-singlet piece is strongly affected by the one-loop QCD correction. In contrast, the QCD correction to the color-octet piece is weak. Once the experiment can measure the branching ratio and energy distribution of the two-charm quark jets in the $\Upsilon$ decay, the result can be used to test the color octet mechanism or give a strong constraint on the color-octet matrix elements.