Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Gluon shadowing in the Glauber-Gribov model at HERA

I. Arsene, L. Bravina, A. Kaidalov, K. Tywoniuk, E. Zabrodin

TL;DR

The paper addresses gluon shadowing in nuclei at small $x$ within a unitarity-respecting Glauber-Gribov framework by summing Pomeron-based multiple scatterings using Schwimmer unitarization. It inputs gluon diffractive parton densities from HERA (DPDFs FIT A/B) and a nucleon gluon distribution (CTEQ6M) to predict the total ${\gamma^*}A$ cross section without free parameters. The main finding is substantial gluon shadowing for heavy nuclei at $x<10^{-3}$ with only mild $Q^2$-dependence, and a shadowing pattern that depends on the diffractive input and the impact-parameter profile; comparisons with other models (FGS, EKS, HKM) show generally stronger shadowing in this framework. The results have important implications for high-energy heavy-ion phenomenology at RHIC/LHC and for ultra-peripheral collisions, and highlight the value of future Electron-Ion Collider measurements for constraining nuclear PDFs.

Abstract

We calculate shadowing using new data on the gluon density of the Pomeron recently measured with high precision at HERA. The calculations are made in a Glauber-Gribov framework and Pomeron tree-diagrams are summed up within a unitarity-conserving procedure. The total cross section of $\vphot A$ interaction is then found in a parameter-free description, employing gluon diffractive and inclusive distribution functions as input. A strong shadowing effect is obtained, in good agreement with several other models. Impact parameter dependence of gluon shadowing is also presented.

Gluon shadowing in the Glauber-Gribov model at HERA

TL;DR

The paper addresses gluon shadowing in nuclei at small within a unitarity-respecting Glauber-Gribov framework by summing Pomeron-based multiple scatterings using Schwimmer unitarization. It inputs gluon diffractive parton densities from HERA (DPDFs FIT A/B) and a nucleon gluon distribution (CTEQ6M) to predict the total cross section without free parameters. The main finding is substantial gluon shadowing for heavy nuclei at with only mild -dependence, and a shadowing pattern that depends on the diffractive input and the impact-parameter profile; comparisons with other models (FGS, EKS, HKM) show generally stronger shadowing in this framework. The results have important implications for high-energy heavy-ion phenomenology at RHIC/LHC and for ultra-peripheral collisions, and highlight the value of future Electron-Ion Collider measurements for constraining nuclear PDFs.

Abstract

We calculate shadowing using new data on the gluon density of the Pomeron recently measured with high precision at HERA. The calculations are made in a Glauber-Gribov framework and Pomeron tree-diagrams are summed up within a unitarity-conserving procedure. The total cross section of interaction is then found in a parameter-free description, employing gluon diffractive and inclusive distribution functions as input. A strong shadowing effect is obtained, in good agreement with several other models. Impact parameter dependence of gluon shadowing is also presented.

Paper Structure

This paper contains 5 sections, 18 equations, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. The Model
  3. Diffractive parton densities from HERA
  4. Numerical results
  5. Conclusions

Figures (6)

  • Figure 1: The single and double scattering contribution to the total ${\gamma^*} N$ cross section.
  • Figure 2: DDIS kinematical variables in the infinite momentum frame.
  • Figure 3: Gluon shadowing for deuteron (dash-dotted curves) and for heavy ions: Ca (dotted curves), Pd (dashed curves), Au (solid curves). Black curves are for FIT A and grey curves are for FIT B.
  • Figure 4: Gluon shadowing for Pb for different virtualities, $Q^2$.
  • Figure 5: Comparison of the results of the Glauber-Gribov model with FGS model fgs03, EKS eks98 and HKM hkm04 parameterizations.
  • ...and 1 more figures