Azimuthal collimation of long range rapidity correlations by strong color fields in high multiplicity hadron-hadron collisions

TL;DR

This paper explains the azimuthal collimation of long-range di-hadron correlations in high multiplicity proton-proton collisions at the LHC using the Color Glass Condensate theory, showing good agreement with experimental data.

Contribution

It demonstrates that CGC effective theory can quantitatively describe azimuthal correlations in high multiplicity p+p collisions and predicts their systematics with varying conditions.

Findings

CGC calculations match CMS di-hadron data

Radial flow is limited in p+p but significant in heavy ion collisions

Predictions for correlation yields with different trigger pT and multiplicity

Abstract

The azimuthal collimation of di-hadrons with large rapidity separations in high multiplicity p+p collisions at the LHC is described in the Color Glass Condensate (CGC) effective theory [1] by N_c^2 suppressed multi-ladder QCD diagrams that are enhanced \alpha_S^(-8) due to gluon saturation in hadron wavefunctions. We show that quantitative computations in the CGC framework are in good agreement with data from the CMS experiment on per trigger di-hadron yields and predict further systematics of these yields with varying trigger pT and charged hadron multiplicity. Radial flow generated by re-scattering is strongly limited by the structure of the p+p di-hadron correlations. In contrast, radial flow explains the systematics of identical measurements in heavy ion collisions.