Ultra-peripheral collisions and hadronic structure

Abstract

Ultra-peripheral collisions are the energy frontier for photon-mediated interactions, reaching, at the Large Hadron Collider (LHC), $\gamma -p$ center of mass energies five to ten times higher than at HERA and reaching $\gamma \gamma$ 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 $3\times 10^{-6}$, 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 $10^{-5}$. 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 $Q^2$. High-statistics ${\rho }^0$ data probe the spatial distribution of the interaction sites; the site distribution is given by the Fourier transform of $d\sigma /dt$. 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).

8 pages, present at Quark Matter 2017 Final version, w/ 1 replaced figure and a few new references

References in corpus (10)

• The Physics of Ultraperipheral Collisions at the LHC
• EPPS16: Nuclear parton distributions with LHC data
• Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC
• Determination of nuclear parton distribution functions and their uncertainties at next-to-leading order
• Revealing proton shape fluctuations with incoherent diffraction at high energy
• Coherent diffractive photoproduction of ${\rho }^0$ mesons on gold nuclei at RHIC
• Observation of Two-source Interference in the Photoproduction Reaction $AuAu\to AuAu{\rho }^0$
• The exclusive $J/\psi$ process at the LHC tamed to probe the low $x$ gluon
• Accessing transverse nucleon and gluon distributions in heavy nuclei using coherent vector meson photoproduction at high energies in ion ultraperipheral collisions
• Two-Photon Interactions with Nuclear Breakup in Relativistic Heavy Ion Collisions

Cited by in corpus (16)

• The Large Hadron-Electron Collider at the HL-LHC
• Imaging the nucleus with high-energy photons
• Photonuclear and Two-photon Interactions at High-Energy Nuclear Colliders
• Coherent J/$\psi$ photoproduction in hadronic heavy-ion collisions
• Exclusive vector meson production at an electron-ion collider
• Inclusive dijet photoproduction in ultraperipheral heavy-ion collisions at the CERN LHC in next-to-leading order QCD
• Nucleon dissociation and incoherent $J/\psi$ photoproduction on nuclei in ion ultraperipheral collisions at the CERN Large Hadron Collider
• Photoproduction of charged final states in ultra-peripheral collisions and electroproduction at an electron-ion collider
• Constraints on nuclear parton distributions from dijet photoproduction at the LHC
• Exclusive photoproduction of vector mesons in proton-lead ultraperipheral collisions at the LHC
• Photoproduction of light vector mesons in Xe-Xe ultraperipheral collisions at the LHC and the nuclear density of Xe-129
• Production of vector mesons in pentaquark states resonance channel in $p$-$A$ ultraperipheral collisions
• Elastic light-by-light scattering in a nonminimal Lorentz violation scenario
• Photoproductions of dileptons, photons, and light vector mesons in p-p, p-Pb, and Pb-Pb collisions at Large Hadron Collider energies
• Heavy-ion collisions - hot QCD in a lab
• Analysis of $J/\psi$ and $\psi (2S)$ Charmonium Production in Ultraperipheral Lead-Lead and Proton-Lead Collisions at LHC Energies