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Quantitative Tests of Color Evaporation: Charmonium Production

J. F. Amundson, O. J. P. Eboli, E. M. Gregores, F. Halzen

TL;DR

The paper tests the color evaporation model for charmonium production across a wide energy range. It argues that color is a nonperturbative degree of freedom and that a perturbatively produced ccbar pair, followed by a universal hadronization fraction, can explain both bound-state and open-charm yields. The authors contrast this with the color-singlet and BB/L formalisms and emphasize that soft gluon exchanges wash out color, allowing a simple, process-independent description. They present the first next-to-leading-order calculation within this model and perform quantitative tests using antiproton/proton, photoproduction, hadroproduction, and Tevatron pT data, finding strong agreement with observations.

Abstract

The color evaporation model simply states that charmonium production is described by the same dynamics as $D \bar D$ production, {\em i.e.}, by the formation of a colored $c \bar c$ pair. Its color happens to be bleached by soft final-state interactions. We show that the model gives a complete picture of charmonium production including low-energy production by proton, photon and antiproton beams, and high-energy production at the Tevatron and HERA. Our analysis includes the first next-to-leading-order calculation in the color evaporation model.

Quantitative Tests of Color Evaporation: Charmonium Production

TL;DR

The paper tests the color evaporation model for charmonium production across a wide energy range. It argues that color is a nonperturbative degree of freedom and that a perturbatively produced ccbar pair, followed by a universal hadronization fraction, can explain both bound-state and open-charm yields. The authors contrast this with the color-singlet and BB/L formalisms and emphasize that soft gluon exchanges wash out color, allowing a simple, process-independent description. They present the first next-to-leading-order calculation within this model and perform quantitative tests using antiproton/proton, photoproduction, hadroproduction, and Tevatron pT data, finding strong agreement with observations.

Abstract

The color evaporation model simply states that charmonium production is described by the same dynamics as production, {\em i.e.}, by the formation of a colored pair. Its color happens to be bleached by soft final-state interactions. We show that the model gives a complete picture of charmonium production including low-energy production by proton, photon and antiproton beams, and high-energy production at the Tevatron and HERA. Our analysis includes the first next-to-leading-order calculation in the color evaporation model.

Paper Structure

This paper contains 3 sections, 3 equations, 3 figures.

Table of Contents

  1. Introduction
  2. The Model
  3. The Tests

Figures (3)

  • Figure 1: Typical diagrams for (a) color singlet $\psi$ production and (b) color evaporation $\psi$ production.
  • Figure 2: Ratio of the cross sections for the production of $J/\psi$ by proton and antiproton beams in the color evaporation model (solid line) and the color singlet model (dashed line) as a function of the center-of-mass energy. Data taken from Ref. exp:ratio.
  • Figure :