J/Psi production in ultraperipheral Pb+Pb and p+Pb collisions at energies available at the CERN Large Hadron Collider

TL;DR

The paper uses two dipole-based descriptions of the dipole–nucleus interaction to predict coherent and incoherent diffractive J/Ψ production in ultraperipheral Pb+Pb and p+Pb collisions at LHC energies. By combining photon flux treatment with amplitude-level calculations that include real-part and skewedness corrections, it compares model predictions to ALICE data and derives robust rapidity dependencies despite normalization sensitivity to the chosen dipole model and vector-meson wavefunction. The fIPsat model with the Gaus-LC wavefunction best matches the coherent data, while both models yield consistent rapidity trends; the work also provides predictions for incoherent production, t-slope distributions, and nuclear-transparency-like ratios in pA and AA collisions. Overall, the approach demonstrates that UPC diffractive J/Ψ observables are powerful probes of the transverse gluon structure in nuclei and can constrain the spatial distribution of gluons when combined with high-energy data from HERA and the LHC.

Abstract

We compute cross sections for incoherent and coherent diffractive J/Psi production in ultraperipheral nucleus-nucleus and proton-nucleus collisions using two different dipole models fitted to HERA data. We obtain a reasonably good description of the available ALICE data for coherent J/Ψproduction and present our prediction for the incoherent cross section. We also find that while the normalization of the cross section depends quite strongly on the dipole model and vector meson wave function used, the rapidity dependence is very well constrained.

Figures (5)

• Figure 1: The coherent diffractive $J/\Psi$ photoproduction ($Q^2=0$ GeV$^2$) cross section in lead-lead collisions at $\sqrt{s_\mathrm{NN}}=2.76$ TeV computed using fIPsat and IIM parametrizations and Boosted Gaussian (thin blue lines) and Gaus-LC (thick black lines) wavefunctions compared with the ALICE data Abelev:2012baMayerCracowTalk:2013.
• Figure 2: The incoherent diffractive $J/\Psi$ photoproduction cross section in lead-lead collisions at $\sqrt{s_\mathrm{NN}}=2.76$ TeV computed using fIPsat and IIM parametrizations and Boosted Gaussian (thin blue lines) and Gaus-LC (thick black lines) wavefunctions.
• Figure 3: The coherent (thick lines) and incoherent (thin lines) diffractive $J/\Psi$ photoproduction cross section in lead-lead collision at $\sqrt{s_{\text{NN}}}=2.76$ TeV as a function of momentum transfer $t$ at midrapidity $y=0$ using the Gaus-LC wave function.
• Figure 4: The diffractive $J/\Psi$ photoproduction cross section in proton-lead collisions at $\sqrt{s_\text{NN}}=5.02$ TeV computed using fIPsat and IIM parametrizations and boosted Gaussian (thin blue lines) and Gaus-LC (thick black lines) wave functions. The proton is moving in the negative $y$ direction.
• Figure 5: Incoherent diffractive $J\Psi$ photoproduction cross section in lead-lead collision normalized by coherent $J/\Psi$ production in pA (nuclear transparency ratio) at $\sqrt{s_\text{NN}}=2.76$ TeV computed using fIPsat and IIM parametrizations and boosted Gaussian (thin blue lines) and Gaus-LC (thick black lines) wave functions. The proton is moving in the negative $y$ direction.