Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Screening Corrections in Photo and DIS Production of $J/Ψ$

E. Gotsman, E. Ferreira, E. Levin, U. Maor, E. Naftali

TL;DR

Exclusive J/Ψ production in photo and DIS probes pQCD validity near the soft-hard boundary at low x. The authors compute forward γ* p → J/Ψ p cross sections within a color-dipole framework, incorporating real-part, skewed-gluon, and Fermi motion corrections, and compare three parameterizations—CTEQ5NSC, GRV98SC, and DL2P—alongside a Regge two-Pomeron model. They find GRV98SC with screening corrections best matches the data across studied kinematics, while CTEQ5NSC overestimates low-energy data and DL2P predicts a notably harder energy dependence at very small x, offering potential discrimination at higher energies. The results constrain gluon dynamics and saturation effects in exclusive vector-meson production and point to future high-energy measurements to sharpen distinctions between pQCD-based and Regge-based descriptions.

Abstract

Photo and DIS production of $J/Ψ$ are investigated and compared with calculations based on pQCD in the LLA approximation without and with screening corrections. The calculation includes corrections induced by the real part of the production amplitude, the skewed (off diagonal) gluon structure function and the relativistic Fermi motion within the charmonium system. Our pQCD results are also compared with the predictions obtained from a Regge type two Pomeron model. Our results suggest some preference for our screened model, but the available data does not enable us to exclude any of the three models we have examined. The properties of these models, when extrapolated to both low and very high energies may provide a more effective discrimination between the different parameterizations.

Screening Corrections in Photo and DIS Production of $J/Ψ$

TL;DR

Exclusive J/Ψ production in photo and DIS probes pQCD validity near the soft-hard boundary at low x. The authors compute forward γ* p → J/Ψ p cross sections within a color-dipole framework, incorporating real-part, skewed-gluon, and Fermi motion corrections, and compare three parameterizations—CTEQ5NSC, GRV98SC, and DL2P—alongside a Regge two-Pomeron model. They find GRV98SC with screening corrections best matches the data across studied kinematics, while CTEQ5NSC overestimates low-energy data and DL2P predicts a notably harder energy dependence at very small x, offering potential discrimination at higher energies. The results constrain gluon dynamics and saturation effects in exclusive vector-meson production and point to future high-energy measurements to sharpen distinctions between pQCD-based and Regge-based descriptions.

Abstract

Photo and DIS production of are investigated and compared with calculations based on pQCD in the LLA approximation without and with screening corrections. The calculation includes corrections induced by the real part of the production amplitude, the skewed (off diagonal) gluon structure function and the relativistic Fermi motion within the charmonium system. Our pQCD results are also compared with the predictions obtained from a Regge type two Pomeron model. Our results suggest some preference for our screened model, but the available data does not enable us to exclude any of the three models we have examined. The properties of these models, when extrapolated to both low and very high energies may provide a more effective discrimination between the different parameterizations.

Paper Structure

This paper contains 3 sections, 10 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Photo and DIS production of $J/\Psi$
  3. Discussion and Conclusions

Figures (5)

  • Figure 1: Photo production of $J/\Psi$ as a function of $W$ and $x$. Data and CTEQ5NSC calculations.
  • Figure 2: Photo production of $J/\Psi$ as a function of $W$ and $x$. Data and GRV98 calculations with and without SC.
  • Figure 3: DIS production of $J/\Psi$. Data and our calculations.
  • Figure 4: The energy dependence of the forward differential slope of $J/\Psi$ photo production. Data and SC calculations with several values of $R^2$.
  • Figure 5: A comparison between the energy dependence predictions of GRV98SC, CTEQ5NSC and DL2P for the integrated cross section of $J/\Psi$ photo production. The available experimental data points are confined within the inner window.