Photoproduction In Ultra-peripheral Pb-Pb Collisions Research Articles

Associated $$\phi $$ and $$J/\Psi $$ photoproduction in ultraperipheral PbPb collisions at the Large Hadron Collider and Future Circular Collider

In this paper we analyze the associated $\phi$ and $J/\Psi$ photoproduction in ultraperipheral $PbPb$ collisions through the double scattering mechanism for the energies of the Large Hadron Collider (LHC) and Future Circular Collider (FCC). Our results complement a previous analysis for the $\rho\rho$, $J/\Psi J/\Psi$ and $\rho J/\Psi$ production. We present our predictions for the total cross sections and rapidity distributions considering the rapidity ranges covered by the ALICE and LHCb detectors, which indicate that a future experimental analysis of $\phi J/\Psi$ final state is feasible. These results point out that the study of the double vector meson photoproduction in heavy ion collisions can be useful to constrain the double scattering mechanism and improve our understanding of the QCD dynamics at high energies.

Inclusive dijet photoproduction in ultraperipheral heavy ion collisions at the CERN Large Hadron Collider in next-to-leading order QCD

We compute the cross section of inclusive dijet photoproduction in ultraperipheral Pb-Pb collisions at the LHC using next-to-leading order perturbative QCD. We demonstrate that our theoretical calculations provide a good description of various kinematic distributions measured by the ATLAS collaboration. We find that the calculated dijet photoproduction cross section is sensitive to nuclear modifications of parton distribution functions (PDFs) at the level of 10 to 20%. Hence, this process can be used to reduce uncertainties in the determination of these nuclear PDFs, whose current magnitude is comparable to the size of the calculated nuclear modifications of the dijet photoproduction cross section.

Coherent J/ψ photoproduction in ultra-peripheral PbPb collisions at [formula omitted] with the CMS experiment

The cross section for coherent J/ψ photoproduction accompanied by at least one neutron on one side of the interaction point and no neutron activity on the other side, Xn0n, is measured with the CMS experiment in ultra-peripheral PbPb collisions at sNN=2.76TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 159μb−1, collected during the 2011 PbPb run. The J/ψ mesons are reconstructed in the dimuon decay channel, while neutrons are detected using zero degree calorimeters. The measured cross section is dσXn0ncoh/dy(J/ψ)=0.36±0.04(stat)±0.04(syst) mb in the rapidity interval 1.8<|y|<2.3. Using a model for the relative rate of coherent photoproduction processes, this Xn0n measurement gives a total coherent photoproduction cross section of dσcoh/dy(J/ψ)=1.82±0.22(stat)±0.20(syst)±0.19(theo) mb. The data strongly disfavor the impulse approximation model prediction, indicating that nuclear effects are needed to describe coherent J/ψ photoproduction in γ+Pb interactions. The data are found to be consistent with the leading twist approximation, which includes nuclear gluon shadowing.

Recent results on ultra-peripheral Pb-Pb and p-Pb collisions at the ALICE experiment

In this paper, we will discuss results on coherent and incoherent J/ψ photoproduction in ultra-peripheral Pb-Pb collisions at = 2.76, as well as preliminary results on exclusive J/ψ and two-photon production in ultra-peripheral p-Pb collisions at = 5.02 TeV. Results on four-pion production in ultra-peripheral Pb-Pb collisions will also be given. Finally, the prospects for other UPC measurements in ALICE will be briefly mentioned.

Coherent J/ψ photoproduction with the ALICE experiment at the LHC

Results from the ALICE experiment on coherent J/ψ photoproduction in ultra-peripheral Pb-Pb collisions at = 2.76 TeV are presented. The J/ψ → μ+μ− channel has been used to measure the cross section in the rapidity interval −3.6 < y < −2.6. The photoproduction cross section has been compared to several theoretical models. The best agreement between data and theoretical predictions is found for models which include nuclear gluon shadowing.