Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5493944 | Nuclear Physics A | 2017 | 8 Pages |
Abstract
Ultra-peripheral collisions are the energy frontier for photon-mediated interactions, reaching, at the Large Hadron Collider (LHC), γâp center of mass energies five to ten times higher than at HERA and reaching γγ energies higher than at LEP. Photoproduction of heavy quarkonium and dijets in pp and pA collisions probes the gluon distribution in protons at Bjorken-x values down to 3Ã10â6, far smaller than can be otherwise studied. In AA collisions, these reactions probe the gluon distributions in heavy ions, down to x values of a few 10â5. Although more theoretical work is needed to nail down all of the uncertainties, inclusion of these data in current parton distribution function fits would greatly improve the accuracy of the gluon distributions at low Bjorken-x and low/moderate Q2. High-statistics Ï0 data probe the spatial distribution of the interaction sites; the site distribution is given by the Fourier transform of dÏ/dt. After introducing UPCs, this review presents recent measurements of dilepton production and light-by-light scattering and recent data on proton and heavy nuclei structure, emphasizing results presented at Quark Matter 2017 (QM2017).
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Nuclear and High Energy Physics
Authors
Spencer R. Klein,