Anisotropic flow measured from multi-particle azimuthal correlations for Pb-Pb collisions at 2.76 TeV by ALICE at the LHC

We report on the measurement of various flow harmonics, $v_n$, with multi-particle cumulants, and present the results from a study of the inter-correlation among different order symmetry planes $\Psi_n$ via multi-particle mixed harmonic correlations. This provides comprehensive experimental information on the fluctuating event-by-event shape of the initial conditions, which is currently among the main sources of large theoretical uncertainties in describing the evolution of the system created in heavy-ion collisions.Comment: 4 pages, 4 figures, Proceedings for Quark Matter 2012, Washington D.C., August 13-18, 201

Recent results on anisotropic flow and related phenomena in ALICE

The exploration of properties of an extreme state of matter, the Quark--Gluon Plasma, has broken new ground with the recent Run 2 operation of the Large Hadron Collider with heavy-ion collisions at the highest energy to date. With the heavy-ion data taken at the end of 2015, the ALICE Collaboration has made the first observation of anisotropic flow of charged particles and related phenomena in lead--lead collisions at the record breaking energy of 5.02 TeV per nucleon pair. The Run 2 results come after the proton-lead collisions, which provided a lot of unexpected results obtained with two- and multi-particle correlation techniques. In these proceedings, a brief overview of these results will be shown. We will discuss how they further enlighten the properties of matter produced in ultrarelativistic nuclear collisions. We indicate the possibility that, to leading order, the striking universality of flow results obtained with correlation techniques in pp, p--A and A--A collisions might have purely mathematical origin, and that physical conclusions therefore could be drawn only from the subleading orders.Comment: 4 pages, 2 figures. Proceedings for Rencontres de Moriond conference, March 19-26, 201

Event-by-event cumulants of azimuthal angles

We develop further the recently proposed event-by-event cumulants of azimuthal angles. The role of reflection symmetry, permutation symmetry, frame independence, and relabeling of particle indices in the cumulant expansion is discussed in detail. We argue that mathematical and statistical properties of cumulants are preserved if cumulants of azimuthal angles are defined event-by-event in terms of single-event averages of azimuthal angles, while they are violated in the traditional approach in which cumulants are defined in terms of all-event averages. We derive for the first time the analytic solutions for the contribution of combinatorial background in the measured 2- and 3-particle correlations. We demonstrate that these solutions for the combinatorial background are universal as they can be written generically in terms of multiplicity-dependent combinatorial weights and marginal probability density functions of starting multivariate distribution. The new general results between multiparticle azimuthal correlators and flow amplitudes and symmetry planes are presented.Comment: 17 pages, 5 figures. Prepared for "Offshell-2021" conferenc

Anisotropic flow of charged particles at sNN=2.76\mathbf{\sqrt{s_{NN}} = 2.76} TeV measured with the ALICE detector

Measurements of anisotropic flow in heavy-ion collisions provide evidence for the creation of strongly interacting matter which appears to behave as an almost ideal fluid. Anisotropic flow signals the presence of multiple interactions and is very sensitive to the initial spatial anisotropy of the overlap region in non-central heavy-ion collisions. In this article we report measurements of elliptic $v_2$, triangular $v_3$, quadrangular $v_4$ and pentagonal $v_5$ flow. These measurements have been performed with 2- and multi-particle correlation techniques.Comment: 4 pages, 4 figures, Quark Matter 2011 proceeding