Evidence for Collective Multiparticle Correlations in p-Pb Collisions

Area of Science:

• High-energy nuclear physics
• Quantum chromodynamics
• Particle physics

Background:

• Proton-lead (p-Pb) and lead-lead (PbPb) collisions probe the behavior of nuclear matter under extreme conditions.
• Previous studies observed long-range correlations in these systems, suggesting a collective phenomenon.

Purpose of the Study:

• To measure the second-order azimuthal anisotropy (v2) using multi-particle correlations in p-Pb and PbPb collisions.
• To investigate the collective origin of long-range correlations by extending analyses to higher-order particle correlations.
• To compare experimental results with theoretical predictions for hydrodynamic behavior in small systems.

Main Methods:

• Analysis of charged particle correlations in p-Pb and PbPb collisions using data from the CMS experiment.
• Application of six- and eight-particle cumulant methods and the Lee-Yang zeros method to extract v2 coefficients.
• Comparison of v2 values from multi-particle correlations with previous two- and four-particle results.

Main Results:

• v2 values extracted from correlations involving six or more particles are consistent with those from four-particle correlations in both p-Pb and PbPb systems.
• The consistency supports the interpretation of a collective origin for long-range correlations.
• Ratios of v2 values are compared to theoretical models, providing insights into hydrodynamic behavior in p-Pb collisions.

Conclusions:

• The study confirms the collective nature of long-range correlations in both p-Pb and PbPb collisions.
• The results provide valuable constraints on theoretical models describing the multiparticle dynamics of small collision systems.
• This research enhances our understanding of the interplay between initial state fluctuations and final state effects in heavy-ion physics.