Anti-Deuteron Production in Upsilon(nS) Decays and the Nearby Continuum

TL;DR

This study measures anti-deuteron production in Upsilon(nS) decays and continuum events, revealing enhanced production in certain decay modes and providing upper limits for others, using CLEO data.

Contribution

It provides the first detailed measurements of anti-deuteron production in Upsilon decays and compares hadronization processes in different decay channels.

Findings

Anti-deuteron production is enhanced in ggg, gg gamma hadronization.

Upper limits are set for Upsilon(4S) decay and continuum production.

Results suggest different hadronization mechanisms in various decay modes.

Abstract

Using CLEO data, we study the production of the anti-deuteron, d-bar, in Upsilon(nS) resonance decays and the nearby continuum. The branching ratios obtained are B^dir(Upsilon(1S) --> d-bar X) = (3.36 +- 0.23 +- 0.25) x 10^-5, B(Upsilon(1S) --> d-bar X) = (2.86 +- 0.19 +- 0.21) x 10^-5, and B(Upsilon(2S) --> d-bar X) = (3.37 +- 0.50 +- 0.25) x 10^-5, where the `dir' superscript indicates that decays produced via re-annihilation of the b bbar pair to a gamma* are removed from both the signal and the normalizing number of Upsilon(1S) decays in order to isolate direct decays of the Upsilon(1S) to ggg, gg gamma. Upper limits at 90% CL are given for B(Upsilon(4S) --> d-bar X) < 1.3 x 10^-5, and continuum production \sigma(e^+e^- --> d-bar X) < 0.031 pb. The Upsilon(2S) data is also used to extract a limit on chi_bJ --> d-bar X. The results indicate enhanced deuteron production in ggg, gg gamma hadronization compared to gamma* --> q qbar. Baryon number compensation is also investigated with the large Upsilon(1S) --> d-bar X sample.