Photoproduction of ρ0 in ultra–peripheral nuclear collisions at ALICE

Kyrre Skjerdal,The Alice Collaboration

doi:10.1088/1742-6596/455/1/012010

Kyrre Skjerdal, The Alice Collaboration

Open Access

https://doi.org/10.1088/1742-6596/455/1/012010

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Abstract

Photoproduction of ρ0 mesons in ultra-peripheral Pb+Pb collisions has been studied by the ALICE Collaboration at the CERN LHC. The strong photon flux associated with relativistic charged nuclei leads to a very large cross section for exclusive photoproduction of ρ0 meson in interactions of the type Pb + Pb → Pb + Pb + ρ0. For a ρ0 produced at mid-rapidity at the LHC, the photon-nucleus center of mass energy is higher than in any previous experiment.The ALICE detector is a general purpose detector dedicated to study heavy-ion collisions. ALICE has excellent performance in the low pT region, and can reconstruct charged particle tracks with 0.1 GeV/c ≤ pT ≤ 100 GeV/c. In this analysis all tracks were required to be within ALICE's central barrel. Analysis of data from the first heavy ion run at the LHC in 2010 will be discussed in this paper.

Highlights

Model predictionsThe center–of–ma√ss energy per nucleon in Pb–Pb collisions at the LHC in the 2010 and 2011 Pb–Pb runs was sNN = 2.76 TeV
The intensity of the electromagnetic field, and the number of virtual photons in the cloud is proportional to Z2, where Z is the charge of the particle [1]
The exclusive photonuclear production of ρ0 has been studied by the ALICE collaboration

Summary

Model predictions

The center–of–ma√ss energy per nucleon in Pb–Pb collisions at the LHC in the 2010 and 2011 Pb–Pb runs was sNN = 2.76 TeV This corresponds to a Lorentz factor of γL = 1470 for each beam in the center of mass system. The model by Frankfurt, Strikman, and Zhalov (GGM (Gribov–Glauber Model )) [3, 4] uses a generalized vector dominance model in the Gribov–Glauber approach It includes non–diagonal transitions, where the photon fluctuates to a ρ , but appear as a ρ0 after scattering off the target nucleus. Its main goal is to study ultra–relativistic heavy–ion collisions It consists of a central barrel, a forward muon arm, and some other smaller forward detectors. To count neutrons from nuclear break up, the Zero Degree Calorimeters (ZDC), which are hadronic calorimeters, located ±116 meters on each side of the interaction point, are used

Data sets and cuts

Findings

Conclusions and outlook