Analysis of the near-side ridge structure in pp collisions via Momentum-Kick Model

TL;DR

This paper demonstrates that the Momentum-Kick Model can effectively explain the near-side ridge structure observed in high-multiplicity proton-proton collisions at LHC energies, challenging the notion that QGP formation is necessary for such phenomena.

Contribution

The study applies and extends the Momentum-Kick Model to high-energy pp collisions, providing a new explanation for the ridge structure without relying on QGP formation.

Findings

MKM successfully reproduces the ridge structure in pp collisions.

The model's multiplicity dependence aligns with experimental data.

Predictions for 14 TeV pp collisions are provided.

Abstract

The near-side ridge structure has been observed in the long-range two-particle correlations in heavy-ion collisions, such as AuAu collisions at the Relativistic Heavy Ion Collider(RHIC) and PbPb collisions at the Large Hadron Collider (LHC). Hydrodynamic models have successfully explained the ridge structure in heavy-ion collisions, indicating the presence of Quark-Gluon Plasma (QGP). Interestingly, similar ridge structures have been detected in high-multiplicity proton-proton and proton-lead collisions, which are classified as small systems in the LHC experiments. Because small systems have been considered insufficient to generate QGP, the applicability of theories developed for heavy-ion collisions to small systems remains controversial. Assuming that kinematic effects play a more significant role in small systems, we expect that the Momentum-Kick Model (MKM) can provide a satisfactory explanation. This model elucidates the long-range and near-side ridge structure in dihadron $\Delta\eta-\Delta\phi$ correlation by explaining that jet particles kick and rearrange medium partons along the direction of the jets. In this study, we apply the MKM to explain high-multiplicity proton-proton collisions at both 13 TeV and 7 TeV in the LHC over various ranges of momenta. Furthermore, we introduce multiplicity dependence in the model to account for the 13 TeV data at various multiplicity ranges. We conclude that the MKM effectively explains the near-side ridge structure observed in proton-proton collisions. The LHC has entered Run 3, achieving higher center-of-mass energies and better luminosity than Run 2. We offer $\Delta\phi$ correlation predictions for pp collisions at 14 TeV and suggest possible extensions of the MKM for future studies.