Implication of two-baryon azimuthal correlations in $pp$ collisions at LHC energies on the QGP

TL;DR

This paper investigates the origin of the near-side depression in two-baryon azimuthal correlations in proton-proton collisions at 7 TeV, suggesting it results from partonic matter expansion and quark coalescence, indicating possible QGP formation.

Contribution

It provides a detailed analysis of the mechanisms behind the correlation depression, emphasizing the role of initial spatial correlations, system expansion, and hadronization processes in small collision systems.

Findings

Finite system expansion causes space-momentum correlations.

Partonic matter with finite lifetime is formed in pp collisions.

The depression feature links to partonic dynamics and hadronization.

Abstract

The near-side depression in two-proton or two-antiproton azimuthal correlations in $pp$ collisions at $\sqrt{s}=$7 TeV has been observed experimentally and then qualitatively reproduced in our earlier studies with a multi-phase transport model. In this study, we further investigate the origin of the depression feature in two-baryon correlations in small collision systems. We find that the initial parton-level spatial correlation, a finite expansion in the parton stage, and quark coalescence are important ingredients leading to the near-side depression. In particular, we find that a finite expansion of the parton system leads to a finite space-momentum correlation at hadronization, which then converts the near-side depression in the coordinate space to that in the momentum space. These results suggest that a partonic matter with a finite lifetime is formed in the pp collisions. Further studies are needed to determine whether the partonic matter is near local equilibrium and can thus be called a QGP or far away from local equilibrium.