Comparison of particle production in quark and gluon fragmentation ats∼10 GeV

Citations Over TimeTop 12% of 2007 papers

Abstract

Using ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{\text{hadrons}}$ data collected with the CLEO-III detector at the Cornell Electron Storage Ring, we study the inclusive production of baryons/antibaryons $(p,\ensuremath{\Lambda})$ and mesons ($\ensuremath{\phi}$ and ${f}_{2}(1270)$) in gluon-fragmentation and quark-fragmentation processes. We first corroborate previous per-event total particle yields in $\ensuremath{\Upsilon}(1\mathrm{S})\ensuremath{\rightarrow}ggg$ compared with nearby continuum (${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}$) indicating greater ($\ensuremath{\sim}\ifmmode\times\else\texttimes\fi{}2$) per-event yields of baryons in 3-gluon fragmentation. We find similar results when we extend that comparison to include the $\ensuremath{\Upsilon}(2\mathrm{S})$ and $\ensuremath{\Upsilon}(3\mathrm{S})$ 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 $\ensuremath{\Upsilon}(1\mathrm{S})\ensuremath{\rightarrow}gg\ensuremath{\gamma}$ with that in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}\ensuremath{\gamma}$ 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 ($\ensuremath{\Upsilon}(1\mathrm{S})\ensuremath{\rightarrow}gg\ensuremath{\gamma}$ compared to ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}\ensuremath{\gamma}$), we find almost no enhancement for protons ($\ensuremath{\sim}1.2\ifmmode\pm\else\textpm\fi{}0.1$), but a significant enhancement ($\ensuremath{\sim}1.9\ifmmode\pm\else\textpm\fi{}0.3$) for $\ensuremath{\Lambda}$'s. This small measured proton enhancement rate is supported by a study of baryon production in ${\ensuremath{\chi}}_{b2}\ensuremath{\rightarrow}gg\ensuremath{\rightarrow}p+X$ relative to ${\ensuremath{\chi}}_{b1}\ensuremath{\rightarrow}q\overline{q}g\ensuremath{\rightarrow}p+X$. Overall, per-event baryon production in radiative two-gluon fragmentation is somewhat smaller than that observed in three-gluon decays of the $\ensuremath{\Upsilon}(1\mathrm{S})$. Our results for baryon production are inconsistent with the predictions of the JETSET (7.3) fragmentation model.

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