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

Abstract

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.

20 pages, 19 figures, to be published in Phys. Rev. C

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• Dynamical evolution of the chiral magnetic effect: Applications to the quark-gluon plasma
• Electric and magnetic response of hot QCD matter
• Anomalous transport model study of chiral magnetic effects in heavy ion collisions
• Isolating the chiral magnetic effect from backgrounds by pair invariant mass
• To CME or not to CME? Implications of p+Pb measurements of the chiral magnetic effect in heavy ion collisions
• Electromagnetic fields from the extended Kharzeev-McLerran-Warringa model in relativistic heavy-ion collisions
• Electromagnetic fields and directed flow in large and small colliding systems at ultrarelativistic energies
• Magnetic-Field Induced Critical Endpoint
• Non-Abelian color fields from relativistic color charge configurations in the classical limit
• Experimental review on the chiral magnetic effect in relativistic heavy ion collisions
• Back-to-back relative-excess observable in search for the chiral magnetic effect
• The Static Heavy Quark-Antiquark Potential within String Theory in Arbitrary Stationary Backgrounds
• Influence of the residual magnetic field on the azimuthal distribution of final-state particles in photon-nuclear processes