ALICE probes of local parity violation with charge dependent azimuthal correlations in Pb-Pb collisions

We report on the measurement of two and three particle azimuthal correlations in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV recorded with ALICE at the LHC. While two particle azimuthal correlations mainly provide an important information on possible background correlations, the three particle correlator probes the charge separation of hadrons with respect to the collision reaction plane which is expected for local parity violation in strong interactions. The two and three particle correlations are presented as a function of collision centrality and differentially vs. pseudorapidity and transverse momentum, and provide strong constraints on the possible mechanism of background (parity conserving) and signal (parity odd) effects in heavy-ion collisions.Comment: Talk given at the 7th Workshop on Particle Correlations and Femtoscopy (WPCF 2011), 20-24 September 2011, Tokyo, Japan; 6 pages, 3 figure

Photon-jet coincidence measurements in polarized pp collisions at sqrt{s}=200 GeV with the STAR Endcap Calorimeter

Recent inclusive measurements with polarized proton-proton collisions at RHIC provide significant constraints on the polarized gluon distribution, Delta g(x), integrated over the gluon momentum range 0.02 < x < 0.3. Di-jet and photon-jet coincidence measurements will allow to study the x-dependence of Delta g(x). In this report we present the status of photon-jet coincidence studies for photons detected at forward pseudorapidity, 1.08<eta<2, using the STAR Endcap Calorimeter.Comment: Talk given at the Tenth Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2009), 26-31 May 2009, San Diego CA, USA; 4 pages, 3 figure

Anisotropic flow and other collective phenomena measured in Pb-Pb collisions with ALICE at the LHC

Recent results of the anisotropic flow measurements by the ALICE Collaboration at the LHC are reviewed. Directed, elliptic, triangular, and quadrangular flow are presented differentially vs. transverse momentum, pseudo-rapidity, and the collision centrality for charged and identified particles. Experimental probes of local parity violation using the charge dependent azimuthal correlations with respect to the reaction plane are also discussed.Comment: Talk given at the International Symposium on Multiparticle Dynamics (ISMD 2011), 26-30 September 2011, AHiroshima (Miyajima Island), Japan; 6 pages, 5 figure

New measurement of pion directed flow relative to the spectator plane by the NA49 experiment at CERN

We report a new measurement of negatively charged pion directed flow $v_1$ relative to the spectator plane for Pb+Pb collisions at the beam energy 40A GeV recorded by the NA49 experiment at CERN. $v_1$ is reported as a function of rapidity and transverse momentum in different classes of collision centrality. The projectile spectator plane is estimated using transverse segmentation of the NA49 forward hadron calorimeter. The new results extend the NA49 data for $v_1$, which was previously measured only relative to the participant plane, and complement recent preliminary data by the NA61/SHINE collaboration and published results from the STAR at RHIC beam energy scan program.Comment: Proceedings of the XIII Workshop on Particle Correlations and Femtoscopy (WPCF 2018), 6 pages, 3 figure

Estimating non-flow effects in measurements of directed flow of protons with the HADES experiment at GSI

Centrality dependence of the directed flow of protons in Au+Au collisions at the beam energy of 1.23A GeV collected by the HADES experiment at GSI is presented. Measurements are performed with respect to the spectators plane estimated using the Forward Wall hodoscope. Biases due to non-flow correlations and correlated detector effects are evaluated. The corresponding systematic uncertainties are quantified using estimates of the spectators plane from various forward rapidity regions constructed from groups of Forward Wall channels and protons reconstructed with the HADES tracking system.Comment: Proceedong for the LXX International conference "NUCLEUS - 2020. Nuclear physics and elementary particle physics. Nuclear physics technologies

Event-by-event background in estimates of the chiral magnetic effect

In terms of the parton-hadron-string-dynamics (PHSD) approach - including the retarded electromagnetic field - we investigate the role of fluctuations of the correlation function in the azimuthal angle $\psi$ of charged hadrons that is expected to be a sensitive signal of local strong parity violation. For the early time we consider fluctuations in the position of charged spectators resulting in electromagnetic field fluctuations as well as in the position of participant baryons defining the event plane. For partonic and hadronic phases in intermediate stages of the interaction we study the possible formation of excited matter in electric charge dipole and quadrupole form as generated by fluctuations. The role of the transverse momentum and local charge conservation laws in the observed azimuthal asymmetry is investigated, too. All these above-mentioned effects are incorporated in our analysis based on event-by-event PHSD calculations. Furthermore, the azimuthal angular correlations from Au+Au collisions observed in the recent STAR measurements within the RHIC Beam-Energy-Scan (BES) program are studied. It is shown that the STAR correlation data at the collision energies of $\sqrt{s_{NN}}$ = 7.7 and 11.5 GeV can be reasonably reproduced within the PHSD. At higher energies the model fails to describe the $\psi$ correlation data resulting in an overestimation of the partonic scalar field involved. We conclude that an additional transverse anisotropy fluctuating source is needed which with a comparable strength acts on both in- and out-of-plane components.Comment: 20 pages, 19 figures, to be published in Phys. Rev.