Cumulant expansion in gluon saturation and five- and six-gluon azimuthal correlations

Abstract

Correlations between the momenta of the final state hadrons measured in proton or nucleus collisions contain information that sheds light on the initial conditions and evolutionary dynamics of the collision system. These correlation measurements have revealed the long-range rapidity correlations in p-p and p-Pb systems, and they have also made it possible to extract the elliptic flow coefficient from hadron correlation measurements. In this work, we calculate five-and six-gluon correlation functions in the framework of saturation physics by using superdiagrams. We also derive the cumulant expansion of the gluon correlators that is valid in the gluon saturation limit. We show that the cumulant expansion of the gluon correlators that is used for counting the number of diagrams to be calculated does not follow the standard cumulant expansion. We also explain how these findings can be used in obtaining experimentally relevant observables such as flow coefficients calculated from correlations as well as ratios of the correlation functions of different orders.

Predictions on three-particle azimuthal correlations in proton--proton collisions

“…[ [29][30][31], we suggested that investigating the three-hadron correlations could rule out one of the two mechanisms.…”

What does the matter created in high multiplicity proton-nucleus collisions teach us about the 3-D structure of the proton?

“…For instance, multiparticle dynamics in the regime of soft momenta p T < Q s,T is sensitive to the dynamics of several color domains of size 1/Q s,T ; in contrast, for p T ≥ Q s,T , the physics is sensitive to dynamics within a given domain. For large p T > Q s,T , the quasiparticle nature of color fields is relevant and the QCD dynamics can be represented in terms of Feynman diagrams, the so-called Glasma graphs [36,37,38,39,40,41,42,43,44]. In the kinematic regime of p T Q s,T , they provide a good description of the ridge.…”