Coherent photoproduction of heavy quarkonia on nuclei

TL;DR

This paper calculates the differential cross section for coherent heavy quarkonia photoproduction on nuclei using the QCD color dipole model, incorporating nuclear shadowing effects and comparing results with ALICE experimental data.

Contribution

It introduces a detailed calculation of nuclear shadowing effects including dipole orientation and gluonic fluctuations within the QCD color dipole framework, advancing understanding of quarkonia production.

Findings

Results agree well with ALICE data on charmonium production.

Includes both higher-twist and leading-twist shadowing effects.

Provides a comprehensive model for coherent photoproduction processes.

Abstract

The differential cross section of coherent photo-production of heavy quarkonia on nuclear targets is calculated within the QCD color dipole formalism. The higher-twist nuclear shadowing corresponding to the $\bar QQ$ Fock component of the photon, is calculated including the correlation between dipole orientation $\vec r$ and impact parameter of a collision $\vec b$, which is related to the transverse momentum transfer via Fourier transform. We also included the leading twist gluon shadowing corresponding to higher Fock components of the photon containing gluons, which have specifically short coherence time, especially for multi-gluon components, even at very high energies. The contribution of such fluctuating gluonic dipole is calculated employing the path-integral technique. Our results are in good agreement with recent ALICE data on charmonium production in ultra-peripheral nuclear collisions.