BFKL evolution and the growth with energy of exclusive J/Psi and Upsilon photo-production cross-sections

TL;DR

This paper assesses whether BFKL evolution can accurately describe the energy dependence of exclusive J/Psi and Upsilon photo-production cross-sections across various high-energy experiments, demonstrating good agreement with data.

Contribution

It demonstrates that BFKL evolution effectively models the energy dependence of exclusive vector meson photo-production cross-sections using a fit to inclusive HERA data.

Findings

BFKL evolution describes the energy dependence well.

Normalization adjustments are needed for impact factor fits.

Data from HERA and LHC are consistent with BFKL predictions.

Abstract

We investigate whether the Balitsky-Fadin-Kuraev-Lipatov (BFKL) low x evolution equation is capable to describe the energy dependence of the exclusive photo-production cross-section of vector mesons J/Psi and Upsilon on protons. Such cross-sections have been measured by both HERA experiments H1 and ZEUS in electron-proton collisions and by LHC experiments ALICE, CMS and LHCb in ultra-peripheral proton-proton and ultra-peripheral proton-lead collisions. Our approach provides a perturbative description of the rise with energy and relies only on a fit of the initial transverse momentum profile of the proton impact factor, which can be extracted from BFKL fits to inclusive HERA data. We find that BFKL evolution is capable to provide a very good description of the energy dependence of the current data set, while the available fits of the proton impact factor require an adjustment in the overall normalization.