Heavy Mesons Photoproduction in Peripheral AA Collisions

TL;DR

This paper investigates heavy vector meson photoproduction in peripheral lead-lead collisions at LHC energies, evaluating the light-cone color dipole formalism's robustness across different regimes and comparing scenarios with experimental data.

Contribution

It introduces a refined model for photon flux and photonuclear cross section in peripheral collisions, extending the ultraperipheral formalism to more central interactions.

Findings

Scenario 3 aligns best with ALICE data, especially in central regions.

The transition from ultraperipheral to peripheral regimes affects the photon flux and cross section.

The model provides a more accurate description of heavy meson production in non-ultraperipheral collisions.

Abstract

The exclusive photoproduction of the heavy vector mesons $\psi$'s and $Y$'s is investigated in peripheral lead-lead collisions for the energies available at the LHC, $\sqrt{s}=2.76$ TeV and $\sqrt{s}=5.02$ TeV. In order to evaluate the robustness of the light-cone color dipole formalism, previously tested in the ultraperipheral regime. It was calculated the rapidity distribution as well as the nuclear modification factor ($R_{AA}$) for the three centrality classes: 30%-50%, 50%-70% and 70%-90%. The transition from ultraperipheral to peripheral regime was carried out sophisticating the photon flux description and the photonuclear cross section, taking into account the effective interaction area. In our calculations, three scenarios were considered: (scenario 1) the direct application of the usual photon flux and of the photonuclear cross section without any relevant change in relation to the UPC's, (scenario 2) the application of an effective photon flux keeping the photonuclear cross section unchanged and (scenario 3) where it was also considered an effective photonuclear cross section. The results obtained from the three scenarios were compared with the ALICE measurements (only $J/\psi$ at the moment), showing a better agreement with the data in the more complete approach (scenario 3), mainly in the more central regions (30%-50% and 50%-70%) where the incertainty is smaller.