V2 Fluctuations Research Articles

Anisotropic flow fluctuations of charged and identified hadrons in Pb-Pb collisions with the ALICE detector

Anisotropic flow fluctuations can be used to constrain the initial conditions and probe the properties and evolution of the system created in heavy-ion collisions. In this proceeding, the pT-differential flow coefficient vn with 2-, 4-, 6- and 8-particle cumulants for charged hadrons are investigated, which allows to study the higher order moments, including skewness and kurtosis, of v2 probability density function (p.d.f.). In addition, the v2 fluctuations of π±, K±, p+p¯, ϕ, KS0, Λ+Λ¯ and Ξ−+Ξ¯+ are also measured at mid rapidity in Pb-Pb collisions at sNN=5.02TeV cumulants. The implications of the results for understanding the properties of the medium are discussed.

Cortical Areas Interact through a Communication Subspace

Most brain functions involve interactions among multiple, distinct areas or nuclei. For instance, visual processing in primates requires the appropriate relaying of signals across many distinct cortical areas. Yet our understanding of how populations of neurons in interconnected brain areas communicate is in its infancy. Here we investigate how trial-to-trial fluctuations of population responses in primary visual cortex (V1) are related to simultaneously recorded population responses in area V2. Using dimensionality reduction methods, we find that V1-V2 interactions occur through a communication subspace: V2 fluctuations are related to a small subset of V1 population activity patterns, distinct from the largest fluctuations shared among neurons within V1. Incontrast, interactions between subpopulations within V1 are less selective. We propose that the communication subspace may be a general, population-level mechanism by which activity can be selectively routed across brain areas.

Elliptic flow fluctuations in Au+Au collisions at GeV

In this talk, we report an analysis of elliptic flow (v2), non-flow (δ2) and v2 fluctuations for the STAR Collaboration at middle rapidity in GeV Au+Au collisions. We compare the results to models of the fluctuations in the initial eccentricity of the overlap zone.

Elliptic flow fluctuations in Au+Au collisions at

We report first measurements of elliptic flow (v2) fluctuations for the STAR collaboration at middle rapidity in collisions. We analyse the multiplicity dependence of the flow vector length distribution to disentangle non-flow correlations from v2 fluctuations. We find that the width of the v2 distribution is approximately 36% of the mean v2 and, within errors, independent of collision centrality. This value coincides with eccentricity fluctuations, apparently leaving little room for other sources of fluctuations.

Physics with identified particles at STAR

New physics results with identified particles at STAR are presented. Measurements at low pT address bulk properties of the collision, while those at high pT address jet energy loss in the bulk matter produced. Between these extremes, measurements at intermediate pT address the interplay between jets and the bulk. We highlight: measurements of v2 fluctuations as a new, sensitive probe of the initial conditions and the equation of state; correlations involving multi-strange particles, along with ratios of identified particles to test coalescence as a mechanism of particle production at intermediate pT; three particle azimuthal correlation to search for conical emission; and the energy and particle-type dependence of hadron production at high pT to study quark and gluon jet energy loss.

Elliptic flow analysis at RHIC with the Lee–Yang zeros method in a relativistic transport approach

The Lee–Yang zeros method is applied to study elliptic flow (v2) in Au+Au collisions at GeV, with the UrQMD model. In this transport approach, the true event plane is known and both the non-flow effects and event-by-event v2 fluctuations exist. Although the low resolutions prohibit the application of the method for most central and peripheral collisions, the integral and differential elliptic flow from the Lee–Yang zeros method agrees with the exact v2 values very well for semi-central collisions.

Third-order conditional transport correlations in the two-dimensional turbulent wake

The far turbulent wake of a cylinder was investigated. Slight heating of the cylinder permitted the use of the conditional sampling technique to gain detailed insight into the transport mechanism. All important third-order correlations of u, v, w, and θ are included. Among the interesting results are that the lateral transport of u2 and v2 fluctuations is three times as intense as that of w2, whereas the streamwise transport of u2 is only twice as intense as that of v2 and w2. On a conditional basis the highest lateral transport is of the v2 component by the intermittent turbulent zones on the wake sides. The conditional lateral transport of the temperature fluctuations by turbulent bulges is especially intense. It is believed that the data will be helpful in refining Reynolds stress closure equations in predictive methodology.