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

Abstract

The ridge signal, which is long-ranged in rapidity, in the di-hadron correlations in high-multiplicity p-p and p-A collisions opened up a whole new research area in high-energy QCD. Although the ridge had been observed in A-A collisions and interpreted as a result of the radial flow of quark-gluon plasma, it had not appeared until recently in the data of small collision systems such as p-p and p-A, nor had it been predicted theoretically or seen in the event generators. There are two competing approaches that attempt to explain the systematics of the di-hadron ridge signal; hydrodynamics and gluon saturation physics (color glass condensate/glasma). In this work, we present predictions for the transverse momentum and rapidity dependence of the three-particle correlation function within the gluon saturation physics. Trihadron correlations can be measured, and the data can possibly rule out one of the two alternative approaches.

Double and triple inclusive gluon production at mid rapidity: quantum interference in p-A scattering

“…Similar effects (albeit with opposite sign) have been later identified in the quark production in the CGC based framework in [9], see also [10,11]. The glasma graph approach was also used in [12,13] to study triple and quadruple gluon correlations. However, these studies were performed in the dilute-dilute limit of glasma graphs which should be only applicable for p-p collisions at midrapidity, while we aim to go beyond this limit and consider p-A.…”

Non-eikonal corrections to multi-particle production in the color glass condensate

“…The double and triple inclusive gluon production cross sections in p-A collisions have been recently studied in [49,50] in the Glasma graph approximation, and in [55] going beyond it, i.e. taking into account multiple scattering effects of the dense target.…”

“…For each observable, the contributions to Bose enhancement of the projectile gluons and HBT contributions of the final state gluons are identified. However, the studies in [49,50,55] are performed within the eikonal approximation without taking into account the corrections due to the finite longitudinal width of the target.…”

“…In the CGC, particle production and correlations have been computed within several approximation schemes, providing an alternative explanation to final state interactions for the ridge phenomenon observed in small systems, proton-proton and proton-nucleus, at the Large Hadron Collider (LHC) at CERN [20][21][22][23][24][25][26][27][28][29][30][31][32][33] and the Relativistic Heavy Ion Collider (RHIC) at BNL [34][35][36][37][38]. The "Glasma graph" approximation [39,40], suitable for collisions between two dilute objects like proton-proton and containing both Bose enhancement and Hanbury-Brown-Twiss effects [41][42][43][44], has been used to describe experimental data [45][46][47][48], and to compute three and four gluon correlations [49,50]. Quark correlations have also been calculated in this framework [51,52].…”

Effect of non-eikonal corrections on azimuthal asymmetries in the color glass condensate

“…For the collision of dilute objects like proton-proton, the "Glasma graph" approximation [27,28], that encodes both Bose enhancement and Hanbury-Brown-Twiss (HBT) effects [29,30,31,32], has been developed and used to describe experimental data [33,34,35,36]. Besides two gluon correlations, those among three and four [37,38] have also been studied, and also those between two quarks [39,40]. The extension to dilute-dense (proton-nucleus) collisions was later done numerically [41] and analytically [42,43,44], including three gluon correlations [43], and applied to describe data [45,46].…”