Elliptic flow contribution to two-particle correlations at different orientations to the reaction plane

Abstract

Collective anisotropic particle flow, a general phenomenon present in relativistic heavy-ion collisions, can be separated from direct particle-particle correlations of different physics origin by virtue of its specific azimuthal pattern. We provide expressions for flow-induced two-particle azimuthal correlations, if one of the particles is detected under fixed directions with respect to the reaction plane. We consider an ideal case when the reaction plane angle is exactly known, as well as present the general expressions in case of finite event-plane resolution. We foresee applications for the study of generic two-particle correlations at large transverse momentum originating from jet fragmentation.

Collective Phenomena in Non-Central Nuclear Collisions

“…Unfortunately, we have not been able to discuss many other important measurements related to the event anisotropy, such as azimuthally sensitive identical and non-identical particle femtoscopic measurements [143,144] (for a recent review, see Ref. [145]) or two particle correlations relative to the reaction plane [129,146].…”

Measurement of event background fluctuations for charged particle jet reconstruction in Pb-Pb collisions at $ \sqrt {{{s_{\text{NN}}}}} = {2}{.76}\,{\text{TeV}} $

“…Three bins are chosen; the out-of-plane orientation where the azimuthal angle between the reconstructed event plane and the cone axis is > 60 • , the in-plane orientation where this angle is < that, for out-of-plane cones, the most probable background p t density is smaller by almost 5 GeV/c relative to the azimuthally averaged estimate of ρ, with opposite effect in-plane. This shift scales with the average flow and the background p t density for a given centrality (∝ v 2 · ρ), and is seen to be sizable in central events, though discrimination of the event plane orientations is limited by finite event-plane resolution [33] and possible biases due to hard jets. The decreasing width of left-hand-side Gaussian is qualitatively consistent with the expectation from reduced particle number fluctuations out-of-plane compared to in-plane.…”

Azimuthally sensitive correlations in nucleus-nucleus collisions

“…It is independent of ∆φ and φ 1 − Φ R . Let us briefly compare the above procedure with the one suggested by Bielcikova et al [27]: these authors show how to analyze correlations in-and out of an event plane, which is not exactly the reaction plane. Since the event-plane resolution is a detector-dependent quantity, this prevents quantitative comparisons between different experiments.…”