Comprehensive studies of $\Upsilon$ inclusive production in $Z$ boson decay

TL;DR

This paper provides a detailed analysis of $$ production in $Z$ decay, incorporating next-to-leading-order QCD corrections and feed-down effects, revealing discrepancies with experimental data.

Contribution

It introduces the first complete NLO calculations of color-octet contributions and evaluates feed-down effects, enhancing the theoretical understanding of $$ production in $Z$ decay.

Findings

Color-octet contributions significantly affect predictions.

Feed-down contributions are substantial and previously neglected.

Theoretical predictions still fall short of experimental measurements.

Abstract

In this paper, we present a comprehensive study of $\Upsilon$ inclusive production in $Z$ boson decay, including the first complete next-to-leading-order calculations of the color-octet (CO) contributions. With the inclusion of the newly-calculated remarkable QCD corrections, the CO processes exhibit crucially phenomenological influence on the existing predictions built on the color-singlet mechanism. We also include the exhaustive evaluations of the feed-down contributions, which remained ignored in the literature, and find them to be considerable. Summing up all the contributions, the $\mathcal{B}_{Z \to \Upsilon(nS)+X}$ still notably undershoot the data released by the L3 Collaboration.