Two-particle azimuthal correlations in photonuclear ultraperipheral Pb+Pb collisions at 5.02 TeV with ATLAS

Rapidity dependence of initial state geometry and momentum correlations in p+Pb collisions

“…More recently, similar signals to those in heavy in collisions have been found in the produced particle spectra of small collision systems, including p/d/ 3 He+A and even p+p [7][8][9][10][11][12] and ultraperipheral Pb+Pb [13] collisions. Such findings have lead to increased research regarding the question how hydrodynamics could possibly be applicable in very small systems that only produce on the order of ten charged hadrons per unit rapidity (see [14] for a review), as well as on the exploration of alternative mechanisms that could generate the observed anisotropies without requiring the creation of a nearly perfect fluid.…”

Azimuthal correlations in photoproduction and deep inelastic ep scattering at HERA

“…Recent measurements of two-particle correlations in photo-nuclear ultra-peripheral Pb+Pb collisions at the LHC [14] have also revealed significant long-range correlations. For a similar kinematic interval ( N ch near 25, p T > 0.5, and |∆η| > 2), the observed two-particle correlation strengths are consistent with the ep photoproduction values seen in figure 4b.…”

“…One of the key observables of the QGP is the collective behaviour of final-state particles. Recent measurements from colliding systems such as p+p, p + A, and photo-nuclear A + A suggest that a QGP may even form in systems previously thought too small to attain thermal equilibrium [7][8][9][10][11][12][13][14]. The deep inelastic scattering of leptons on protons produces even smaller systems.…”

Mining for Gluon Saturation at Colliders

“…It might also be possible to single out saturation effects by studying azimuthal correlations in the diffractive production of dihadron or dijets. This subject has been investigated recently for DIS and UPCs in [90][91][92][93][94][95].…”