Comparison of particle production in quark and gluon fragmentation at s10GeV

R. A. Briere et al. (CLEO Collaboration)
Phys. Rev. D 76, 012005 – Published 27 July 2007

Abstract

Using e+ehadrons data collected with the CLEO-III detector at the Cornell Electron Storage Ring, we study the inclusive production of baryons/antibaryons (p,Λ) and mesons (ϕ and f2(1270)) in gluon-fragmentation and quark-fragmentation processes. We first corroborate previous per-event total particle yields in Υ(1S)ggg compared with nearby continuum (e+eqq¯) indicating greater (×2) per-event yields of baryons in 3-gluon fragmentation. We find similar results when we extend that comparison to include the Υ(2S) and Υ(3S) resonances. With higher statistics, we now also probe the momentum dependence of these per-event particle yields. Next, we compare particle production in the photon-tagged process Υ(1S)ggγ with that in e+eqq¯γ events, to allow comparison of two-parton with three-parton particle-specific fragmentation. For each particle, we determine the “enhancement” ratio, defined as the ratio of particle yields per gluon-fragmentation event compared to quark-fragmentation event. Thus defined, an enhancement of 1.0 implies equal per-event production in gluon and quark fragmentation. In the photon-tagged analysis (Υ(1S)ggγ compared to e+eqq¯γ), we find almost no enhancement for protons (1.2±0.1), but a significant enhancement (1.9±0.3) for Λ’s. This small measured proton enhancement rate is supported by a study of baryon production in χb2ggp+X relative to χb1qq¯gp+X. Overall, per-event baryon production in radiative two-gluon fragmentation is somewhat smaller than that observed in three-gluon decays of the Υ(1S). Our results for baryon production are inconsistent with the predictions of the JETSET (7.3) fragmentation model.

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  • Received 19 April 2007

DOI:https://doi.org/10.1103/PhysRevD.76.012005

©2007 American Physical Society

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Vol. 76, Iss. 1 — 1 July 2007

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