Flow dominance and factorization of transverse momentum correlations in Pb-Pb collisions at the LHC

Abstract

We present the first measurement of the two-particle transverse momentum differential correlation function, $P_2\equiv ⟨\Delta p_{\mathrm{T}}\Delta p_{\mathrm{T}}⟩/⟨p_{\mathrm{T}}{⟩}^2$, in Pb-Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 2.76 TeV. Results for $P_2$ are reported as a function of relative pseudorapidity ($\Delta \eta$) and azimuthal angle ($\Delta \phi$) between two particles for different collision centralities. The $\Delta \varphi$ dependence is found to be largely independent of $\Delta \eta$ for $|\Delta \eta |\ge$ 0.9. In 5% most central Pb-Pb collisions, the two-particle transverse momentum correlation function exhibits a clear double-hump structure around $\Delta \phi =\pi$ (i.e., on the away side), which is not observed in number correlations in the same centrality range, and thus provides an indication of the dominance of triangular flow in this collision centrality. Fourier decompositions of $P_2$, studied as a function of collision centrality, show that correlations at $|\Delta \eta |\ge$ 0.9 can be well reproduced by a flow ansatz based on the notion that measured momentum correlations are strictly determined by the collective motion of the system.

16 pages, 3 captioned figures, authors from page 11, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/3420

References in corpus (7)

• Elliptic flow of identified hadrons in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Event-by-event mean $p_{\mathrm{T}}$ fluctuations in pp and Pb-Pb collisions at the LHC
• Collective phenomena in non-central nuclear collisions
• Pseudorapidity dependence of the anisotropic flow of charged particles in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV
• Methods for the Study of Transverse Momentum Differential Correlations
• Evolution of the longitudinal and azimuthal structure of the near-side jet peak in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV
• Correction methods for finite-acceptance effects in two-particle correlation analyses

Cited by in corpus (11)

• The ALICE experiment: a journey through QCD
• Collision Energy Dependence of $p_{\mathrm{t}}$ Correlations in Au+Au Collisions at RHIC
• Two particle differential transverse momentum and number density correlations in p-Pb and Pb-Pb at the LHC
• Differential two-particle number and momentum correlations with the AMPT, UrQMD, and EPOS models in Pb-Pb collisions at $\sqrt{{\text{s}}_{{}_{\mathrm{NN}}}}$= 2.76 TeV
• General balance functions of identified charged hadron pairs of $(\pi ,\mathrm{K},\mathrm{p})$ in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV
• Simulation studies of ${\mathrm{R}}_2(\mathrm{\Delta }\eta ,\mathrm{\Delta }\phi )$ and ${\mathrm{P}}_2(\mathrm{\Delta }\eta ,\mathrm{\Delta }\phi )$ correlation functions in pp collisions with the PYTHIA and HERWIG models
• Review of nonflow estimation methods and uncertainties in relativistic heavy-ion collisions
• System size and energy dependence of the mean transverse momentum fluctuations at the LHC
• Azimuthal dependence of two-particle transverse momentum current correlations
• Measurements of differential two-particle number and transverse momentum correlation functions in pp collisions at $\sqrt{\text{s}}$ = 13 TeV
• Balance functions of charged hadron pairs $(\pi ,K,p)\otimes (\pi ,K,p)$ in Pb--Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$2.76 TeV