On the presence of nonjet "higher harmonic" components in 2D angular correlations from high energy heavy ion collisions

Abstract

It is conjectured that several higher harmonic flows $v_m$ may result from initial-state geometry fluctuations in åcollisions coupled to a radially-expanding medium. But as with "elliptic flow" $v_2$ measurements, non-hydrodynamic mechanisms such as jet production may contribute to other higher azimuth multipoles $v_m$ as biases. Careful distinctions should be maintained between jet-related and nonjet (possibly hydrodynamic) contributions to $v_m$ (e.g., "nonflow" and "flow"). In this study we consider several questions: (a) To what extent do jet-like structures in two-dimensional (2D) angular correlations contribute to azimuth multipoles inferred from various $v_m$ methods? (b) If a multipole element is added to a 2D fit model is a nonzero amplitude indicative of a corresponding flow component? and (c) Can 2D correlations establish the necessity of nonjet contributions to some or all higher multipoles? Model fits to 2D angular correlations are used to establish the origins of azimuth multipoles inferred from 1D projections onto azimuth or from nongraphical numerical methods. We find that jet-like angular correlations, and specifically a 2D peak at the angular origin consistent with jet production, constitute the dominant contribution to inferred higher multipoles, and the data do not {\em require} higher multipoles in isolation from the jet-like 2D peak. Inference of "higher harmonic flows" results from identifying certain nominally jet-like structure as flow manifestations through unjustified application of 1D Fourier series analysis. Although the peak structure at the angular origin is strongly modified in more-central collisions some properties remain compatible with relevant pQCD theory expectations for jet production.

14 pages, 11 figures

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Cited by in corpus (7)

• Third Harmonic Flow of Charged Particles in Au+Au Collisions at sqrtsNN = 200 GeV
• Beam energy dependence of Elliptic and Triangular flow with the AMPT model
• Centrality dependence of chemical freeze-out parameters from net-proton and net-charge fluctuations using hadron resonance gas model
• CCharge-multiplicity dependence of single-particle transverse-rapidity ${\mathbf{y}}_{\mathbf{t}}$ and pseudorapidity $\eta$ densities and 2D angular correlations from 200 GeV $p$-$p$ collisions
• A critical review of RHIC experimental results
• Optimal modeling of 1D azimuth correlations in the context of Bayesian inference
• Challenging the utility of third-order azimuth harmonics in the description of ultra-relativistic heavy-ion collisions