Speaker
Description
The suppression of the away-side peak in azimuthal correlations of forward di-hadrons in d+Au vs. p+p collisions observed at RHIC remains one of the most striking experimental evidences supporting the saturation regime of quantum chromodynamics. Within the Color Glass Condensate (CGC) framework, we improve the state-of-the-art description of this observable, by deriving a cross section for the production of hadron pairs in the back-to-back limit. In this configuration, the cross section is manifestly factorized into a dilute component, the projectile proton, described by standard collinear parton distribution functions, and a dense counterpart, the saturated nuclear target, which is described by means of transverse-momentum-dependent gluon distributions, whose small-x evolution we obtain by solving the running-coupling Balitsky-Kovchegov equation. This formalism has proven able to accurately capture the suppression of the away-side peak observed in RHIC data.
Starting from this approach, then, we argue that the forward two-particle correlation function measured by the LHCb Collaboration in central p+Pb collisions at $\sqrt{s}=5.02$ TeV is amenable to a CGC description. In particular, we show that the away-side peak observed at LHCb can be decomposed into a double-ridge structure - whose origin is not our concern - and a di-jet structure, whose away-side peak is sensitive to parton saturation effects. We show that our formalism correctly describes the away-side peak measured at LHCb in p+Pb collisions, and we make predictions upcoming p+p data at 5 TeV. Comparing our results in p+p to LHCb data, the observation made at RHIC is replicated: We predict a visible suppression of the away-side peak in forward p+Pb collisions at LHC energies. This finding, if confirmed in experiment, would end up providing the best evidence in favor of QCD saturation in LHC data.
| Content type | Theory |
|---|---|
| Centralised submission by Collaboration | Presenter name already specified |
