Angular and long range rapidity correlations in particle production at high energy

TL;DR

This paper explores the origin of long-range rapidity and angular correlations, known as the 'ridge', in high energy collisions, emphasizing the role of gluon saturation and Pomeron loops in high energy QCD.

Contribution

It provides a comprehensive analysis of the mechanisms behind the ridge effect, highlighting the significance of gluon saturation and Pomeron loops in high energy QCD.

Findings

The ridge effect naturally arises in high energy QCD due to gluon saturation.

Gluon saturation and Pomeron loops are crucial for understanding long-range correlations.

The analysis emphasizes the importance of $N_c$ counting in practical realizations.

Abstract

We discuss the general mechanism leading to long-range rapidity and angular correlations produced in high energy collisions (the "ridge"). This effect naturally appears in the high energy QCD and is strongly sensitive to physics of the gluon saturation. We comment on various recent practical realizations of the main idea, paying special attention to $N_c$ counting and stress the relevance of Pomeron loops.