Comparison of particle production in quark and gluon fragmentation at root s similar to 10 GeV
Physical Review D 76,1 (2007)
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Using e(+)e(-)-> hadrons data collected with the CLEO-III detector at the Cornell Electron Storage Ring, we study the inclusive production of baryons/antibaryons (p,Lambda) and mesons (phi and f(2)(1270)) in gluon-fragmentation and quark-fragmentation processes. We first corroborate previous per-event total particle yields in Upsilon(1S)-> ggg compared with nearby continuum (e(+)e(-)-> q (q) over bar) indicating greater (similar to x2) per-event yields of baryons in 3-gluon fragmentation. We find similar results when we extend that comparison to include the Upsilon(2S) and Upsilon(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 Upsilon(1S)-> gg gamma with that in e(+)e(-)-> q (q) over bar 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 (Upsilon(1S)-> gg gamma compared to e(+)e(-)-> q (q) over bar gamma), we find almost no enhancement for protons (similar to 1.2 +/- 0.1), but a significant enhancement (similar to 1.9 +/- 0.3) for Lambda's. This small measured proton enhancement rate is supported by a study of baryon production in chi(b2)-> gg -> p+X relative to chi(b1)-> q (q) over barg -> p+X. Overall, per-event baryon production in radiative two-gluon fragmentation is somewhat smaller than that observed in three-gluon decays of the Upsilon(1S). Our results for baryon production are inconsistent with the predictions of the JETSET (7.3) fragmentation model.
Astronomy & Astrophysics;; Physics, Particles & Fields
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