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

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&#39; 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 σ(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.