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$J/ψ+ c + \bar{c}$ Photoproduction in $e^+ e^-$ Scattering

Cong-Feng Qiao, Jian-Xiong Wang

TL;DR

The paper investigates $J/\psi$ production in $e^+e^-$ collisions by adding the subleading direct process $\gamma\gamma \rightarrow J/\psi+c+\bar{c}$ to LEP II analyses. Using Weizsäcker-Williams photon flux, NRQCD CS projections, and a full Feynman-diagram calculation via FDC, it demonstrates that this channel yields a significant contribution at moderate to high $p_T$ and cannot be captured by simple fragmentation. While it helps bridge part of the gap between theory and DELPHI data, it does not fully resolve the discrepancies, underscoring substantial theoretical uncertainties and the potential importance of NLO corrections for robust NRQCD universality tests. The results suggest that future Linear Colliders could observe this process with good precision, providing a crucial test of quarkonium production mechanisms.

Abstract

We investigate the $J/ψ$ + c + $\bar{c}$ photoproduction in $e^+ e^-$ collision at the LEP II energy. The physical motivations for this study are: 1) such next-to-leading order(NLO) process was not considered in previous investigations of $J/ψ$ photoproduction in $e^+ e^-$ interaction, and it is worthwhile to do so in order to make sound predictions for experimental comparison; 2) from recent Belle experiment results, the process with same final states at the $B$ factory has a theoretically yet unexplainable large fraction; hence it is interesting to see what may happen at other colliders; 3) the existing LEP data are marginal in observing such process, and at the planed Linear Colliders(LCs) this process can be measured with high accuracy; 4) it is necessary to take this process into consideration in the aim of elucidating the quarkonium production mechanism, especially in testing the universality of NRQCD nonperturbative matrix elements via $J/ψ$ photoproduction in electron-position collisions.

$J/ψ+ c + \bar{c}$ Photoproduction in $e^+ e^-$ Scattering

TL;DR

The paper investigates production in collisions by adding the subleading direct process to LEP II analyses. Using Weizsäcker-Williams photon flux, NRQCD CS projections, and a full Feynman-diagram calculation via FDC, it demonstrates that this channel yields a significant contribution at moderate to high and cannot be captured by simple fragmentation. While it helps bridge part of the gap between theory and DELPHI data, it does not fully resolve the discrepancies, underscoring substantial theoretical uncertainties and the potential importance of NLO corrections for robust NRQCD universality tests. The results suggest that future Linear Colliders could observe this process with good precision, providing a crucial test of quarkonium production mechanisms.

Abstract

We investigate the + c + photoproduction in collision at the LEP II energy. The physical motivations for this study are: 1) such next-to-leading order(NLO) process was not considered in previous investigations of photoproduction in interaction, and it is worthwhile to do so in order to make sound predictions for experimental comparison; 2) from recent Belle experiment results, the process with same final states at the factory has a theoretically yet unexplainable large fraction; hence it is interesting to see what may happen at other colliders; 3) the existing LEP data are marginal in observing such process, and at the planed Linear Colliders(LCs) this process can be measured with high accuracy; 4) it is necessary to take this process into consideration in the aim of elucidating the quarkonium production mechanism, especially in testing the universality of NRQCD nonperturbative matrix elements via photoproduction in electron-position collisions.

Paper Structure

This paper contains 4 sections, 42 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Physics Motivation and Formalism
  3. Numerical Results
  4. Discussion and Conclusions

Figures (3)

  • Figure 1: Half of the Feynman diagrams of discussed $J/\psi$ producing subprocess, $\gamma + \gamma \rightarrow J/\psi + c+ \bar{c}$. The missing part of diagrams are the charge conjugation of the shown ones, and can be simply obtained by flipping the fermion flow directions.
  • Figure 2: The transverse momentum distribution of $J/\psi$ photoproduction in LEP II experiment. The results of $\gamma + \gamma \rightarrow J/\psi + c+ \bar{c}$ process are confronted with the central values in previous study in Ref. klasen:yr02 and recent DELPHI experimental result delphi:yr01.
  • Figure 3: From the upper left to lower right, it is the plot of mass distribution, $d\sigma/dM_{\gamma\gamma}$; angular distribution, $d\sigma/d\cos\theta$; rapidity distribution, $d\sigma/d y$; pseudo-rapidity distribution, $d\sigma/d\eta$.