Mass Ordering of Spectra from Fragmentation of Saturated Gluon States in High-Multiplicity Proton-Proton Collisions

Importance of initial and final state effects for azimuthal correlations in p+Pb collisions

“…While calculations within the hydrodynamic framework have been quite successful in describing observables in these small collision systems, alternative explanations relying entirely on intrinsic momentum correlations of the produced particles can also reproduce many features of the experimental data. This includes two and more particle azimuthal correlations and their p T dependence [5][6][7] and mass splitting of identified particle v n [8]. Apart from the existence of alternative explanations, the applicability of hydrodynamics becomes increasingly doubtful as the system size decreases and gradients increase.…”

“…The initial gluon distributions [14,15] from the IP-Glasma model are anisotropic in momentum space [8,16,17], thus contain the intrinsic momentum space correlations of the color glass condensate (CGC) picture [18,19]. Final state interactions mediated by perturbative quantum chromo dynamic (pQCD) cross sections are then simulated microscopically in BAMPS.…”

What does the matter created in high multiplicity proton-nucleus collisions teach us about the 3-D structure of the proton?

“…This was done in [53] where it was shown that significant v 2,3 (p T ) of gluons is generated in pA collisions. In [54], an event generator was developed whereby gluons produced in the Yang-Mills evolution were fragmented using the Lund string fragmentation algorithm [55,56]. This CGC+PYTHIA framework, applied to high multiplicity pp collisions generates the near-side ridge observed in experiments.…”

Energy independent scaling of the ridge and final state description of high multiplicity p+p collisions at s=7 and 13 TeV

“…In heavy ion collisions [5][6][7][8] such long-range correlations are attributed to hydrodynamical response of a strongly interacting system to the initial spatial anisotropy. However, the origin of such correlations in small collision systems is debated to be either driven by hydrodynamic response of initial state geometry [9][10][11][12][13] or due to intrinsic momentum space correlations among the initially produced patrons [14][15][16][17]. Assuming the applicability of hydrodynamics [18][19][20][21] one can explain several experimental observations in high multiplicity p þ p and p þ Pb collisions at LHC energies [9][10][11]13].…”

“…Alternative approaches based on purely initial state models and percolation of strings along with quenching of the partons can also explain several qualitative and quantitative features of the ridgelike correlations over a wide range of systems and energies [28][29][30][31][32][33][34][35][36][37][38]. Models such as CGC+PYTHIA [15] have demonstrated that initial state correlations in momentum space generated as a consequence of gluon saturation can survive fragmentation and explain the mass ordering of flow harmonics, mean transverse momentum (hp T i) in high multiplicity p þ p collisions at the LHC energy.…”