Pseudorapidity dependence of long-range two-particle correlations in pPb collisions at sqrt(s[NN]) = 5.02 TeV

TL;DR

This study investigates how long-range two-particle correlations vary with pseudorapidity in pPb collisions at 5.02 TeV, revealing asymmetric v2 behavior and insights into collective effects in high-multiplicity events.

Contribution

It provides the first detailed analysis of pseudorapidity dependence of flow coefficients in pPb collisions, highlighting asymmetries in v2 and the persistence of collective behavior at large pseudorapidity separations.

Findings

Normalized v2 decreases at forward pseudorapidity, indicating asymmetry.

No significant pseudorapidity dependence observed for v3.

Collective effects are present in high-multiplicity pPb collisions.

Abstract

Two-particle correlations in pPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV are studied as a function of the pseudorapidity separation (Delta eta) of the particle pair at small relative azimuthal angle (abs(Delta phi) < pi/3). The correlations are decomposed into a jet component that dominates the short-range correlations (abs(Delta eta) < 1), and a component that persists at large Delta eta and may originate from collective behavior of the produced system. The events are classified in terms of the multiplicity of the produced particles. Finite azimuthal anisotropies are observed in high-multiplicity events. The second and third Fourier components of the particle-pair azimuthal correlations, V[2] and V[3], are extracted after subtraction of the jet component. The single-particle anisotropy parameters v[2] and v[3] are normalized by their lab frame mid-rapidity value and are studied as a function of eta[cm]. The normalized v[2] distribution is found to be asymmetric about eta[cm] = 0, with smaller values observed at forward pseudorapidity, corresponding to the direction of the proton beam, while no significant pseudorapidity dependence is observed for the normalized v[3] distribution within the statistical uncertainties.