[Paper Review] Correlations in multiparticle production

Sergey Troshin, N. E. Tyurin|arXiv (Cornell University)|Aug 21, 2011

High-Energy Particle Collisions Research3 citations

TL;DR

The paper proposes that the ridge-like structure in two-particle correlations observed in high-multiplicity pp collisions at the LHC arises from coherent rotation of a transient, deconfined quark-pion liquid formed in peripheral collisions. This rotation, driven by initial orbital angular momentum and strong interactions, produces narrow Δϕ correlations and broad Δη distributions, explaining collective behavior typically seen in heavy-ion collisions.

ABSTRACT

We discuss correlations in the hadron production in the $pp$-collision with emphasize on the ridge-like structure origin in the two-particle correlation function. We suggest that this structure can appear due to a rotating nature of the transient state of matter generated in the intermidiate stage of proton collison.

Motivation & Objective

• To explain the origin of ridge-like structures in two-particle correlation functions observed in high-multiplicity pp collisions at √s = 7 TeV.
• To investigate whether collective effects in pp collisions—previously seen only in heavy-ion collisions—can be explained by a rotating transient state of matter.
• To explore the role of orbital angular momentum and unitarity in generating coherent, collective dynamics in hadron collisions.
• To connect experimental observables such as directed flow (v₁), elliptic flow (v₂), and mean transverse momentum to the rotating transient matter model.
• To assess whether the observed phenomena indicate a deconfined, strongly interacting state resembling quark-gluon plasma in elementary pp collisions.

Proposed method

• Modeling the transient state in pp collisions as a rotating liquid of massive quarks and pions formed in the overlap region at non-zero impact parameters.
• Using the inelastic overlap function h_inel(s,b) to show that high-multiplicity events are dominated by peripheral collisions with non-zero impact parameters.
• Applying the unitarity condition Im f(s,b) = h_el(s,b) + h_inel(s,b) to relate inelastic amplitudes to the dynamics of the transient state.
• Linking the coherent rotation of the quark-pion system to narrow Δϕ and broad Δη correlations in two-particle correlation functions.
• Deriving a linear relation ⟨p_T⟩(s) = a + b⟨n⟩(s) between mean transverse momentum and mean multiplicity, consistent with experimental data.
• Analyzing the influence of rotation on collective flow coefficients v₁ and v₂, and on particle emission anisotropy.

Experimental results

Research questions

• RQ1 Can the ridge-like structure in pp collisions at LHC energies be explained by coherent rotation of a transient quark-pion liquid?
• RQ2 What is the role of initial orbital angular momentum in generating collective behavior in high-multiplicity pp events?
• RQ3 How does the rotating transient state reproduce the observed two-particle correlation patterns (narrow Δϕ, broad Δη)?
• RQ4 To what extent do the observed collective effects (e.g., v₁, v₂, ⟨p_T⟩) in pp collisions align with predictions from a rotating, deconfined matter model?
• RQ5 Does the presence of such collective effects imply that the matter produced in pp collisions shares properties with the quark-gluon plasma observed in heavy-ion collisions?

Key findings

• The ridge-like structure in two-particle correlations in pp collisions arises from coherent rotation of a transient quark-pion liquid formed in peripheral collisions.
• High-multiplicity events at √s = 7 TeV are dynamically selected from peripheral impact parameters due to the shape of the inelastic overlap function h_inel(s,b).
• The narrow Δϕ and broad Δη correlation structure is a direct consequence of the collective rotation of the transient matter in the xz-plane.
• The model predicts a linear dependence ⟨p_T⟩(s) = a + b⟨n⟩(s), which is in good agreement with existing experimental data on mean transverse momentum and multiplicity.
• The mechanism naturally explains directed flow (v₁) and elliptic flow (v₂) as signatures of rotational dynamics in the transient state.
• The simultaneous appearance of anisotropic flows and secondary particle polarization supports the interpretation of a genuine deconfined, strongly interacting state in pp collisions, with orbital angular momentum as the key driver.