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NLO Quarkonium Production in Hadronic Collisions

M. L. Mangano, A. Petrelli

TL;DR

This paper investigates next-to-leading order QCD corrections to quarkonium production in hadronic collisions within the NRQCD framework, focusing on both color-singlet and color-octet contributions. Using dimensional regularization and universal soft/collinear factorization, it derives the general NLO structure across gg, qg, and qq channels and reports preliminary results for P-wave states, revealing very large and sometimes negative corrections at collider energies. The findings underscore significant issues with perturbative reliability at high energies, sensitivity to small-x gluon densities, and the need for improved fragmentation treatments and exclusive final-state modeling. The work also discusses how fragmentation and phase-space constraints influence high-p_t predictions and outlines directions for future theoretical and MC developments to refine NRQCD-based predictions.

Abstract

We present some preliminary results on the next-to-leading order calculation in QCD of quarkonium production cross sections in hadronic collisions. We will show that the NLO total cross sections for $P$-wave states produced at high energy are not reliable, due to the appearance of very large and negative contributions. We also discuss some issues related to the structure of final states in colour-octet production and to high-p_T fragmentation.

NLO Quarkonium Production in Hadronic Collisions

TL;DR

This paper investigates next-to-leading order QCD corrections to quarkonium production in hadronic collisions within the NRQCD framework, focusing on both color-singlet and color-octet contributions. Using dimensional regularization and universal soft/collinear factorization, it derives the general NLO structure across gg, qg, and qq channels and reports preliminary results for P-wave states, revealing very large and sometimes negative corrections at collider energies. The findings underscore significant issues with perturbative reliability at high energies, sensitivity to small-x gluon densities, and the need for improved fragmentation treatments and exclusive final-state modeling. The work also discusses how fragmentation and phase-space constraints influence high-p_t predictions and outlines directions for future theoretical and MC developments to refine NRQCD-based predictions.

Abstract

We present some preliminary results on the next-to-leading order calculation in QCD of quarkonium production cross sections in hadronic collisions. We will show that the NLO total cross sections for -wave states produced at high energy are not reliable, due to the appearance of very large and negative contributions. We also discuss some issues related to the structure of final states in colour-octet production and to high-p_T fragmentation.

Paper Structure

This paper contains 4 sections, 15 equations, 2 figures.

Table of Contents

  1. Introduction
  2. The Structure of Quarkonium Total Cross Sections
  3. Numerical Results
  4. Concluding Remarks

Figures (2)

  • Figure 1: Total cross section for $pp\hbox{$\rightarrow$} \chi_2X$ as a function of beam energy for fixed-target collisions (a), and as a function of $\sqrt{S}$ for collider configurations (b).
  • Figure 2: Left: total cross section for $pp\hbox{$\rightarrow$} \chi_{c,2}X$ as a function of $\sqrt{S}$ with PDF set MRSA. Total cross section for $pp\hbox{$\rightarrow$} \chi_{b,2}X$ as a function of $\sqrt{S}$ with PDF set MRSA.