Abstract
In this paper, we discuss the exclusive photoproduction of ground and excited states of $\psi(1S,2S)$ and $\Upsilon(1S,2S)$ in ultraperipheral collisions (UPCs). Using the potential model in order to obtain the vector meson wave function, we find a good agreement of our calculations with data from the LHC and HERA colliders for $J/\psi (1S,2S) $ and $\Upsilon(1S)$ in $\gamma p$ collisions. We extend the calculations to the nuclear target case applying them to $AA$ UPCs with the use of the shadowing and finite coherence length effects fitted to the data. Our results are compared to the recent LHC data, in both incoherent ($J/\Psi(1S)$ at 2.76 TeV) and coherent ($J/\Psi(1S)$ at 2.76 and 5.02 TeV) processes. We also show the corresponding predictions for the excited states, in the hope that future measurements could provide more detailed information about the vector meson wave functions and nuclear effects.
Highlights
Phenomenology of exclusive quarkonia photoproduction processes offers very sensitive and powerful probes for the associated soft and hard QCD phenomena
We extend the calculations to the nuclear target case applying them to AA ultraperipheral collisions (UPCs) with the use of the shadowing and finite coherence length effects fitted to the data
Charmonia ψð1S; 2SÞ photoproduction probes predominantly nonperturbative phenomena at a semihard scale. This means that a simultaneous description of the existing charmonia and bottomonia photoproduction data is required for validation of the universality of the quarkonia production mechanism that is expected to incorporate both hard and soft QCD effects on the same footing
Summary
Phenomenology of exclusive quarkonia photoproduction processes offers very sensitive and powerful probes for the associated soft and hard QCD phenomena. Lowest Fock state of the photon in the light-front (LF) (or infinite-momentum) frame, γ → QQ Such an assumption about a photonlike LF quarkonium wave function is unjustified as the corresponding rest-frame wave function necessarily has an admixture of a D-wave component whose weight cannot be established in the framework of a suitable interquark interaction potential [25]. Such an uncontrollable D-wave contribution has a considerable impact on quarkonia photoproduction observables as was recently advocated in Ref.
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