Searches for Chiral Magnetic Effect and Chiral Magnetic Wave in Xe-Xe and Pb-Pb collisions with ALICE

Abstract

An important property of the strong interaction which is potentially observable in heavy-ion collisions is local parity violation. It manifests as a charge separation along the direction of the magnetic field, a phenomenon called the Chiral Magnetic Effect (CME). A similar effect in which the presence of a vector charge (e.g., electric charge) causes a separation of chiralities is the Chiral Separation Effect (CSE). Their coupling leads to a wave propagation of the electric charge called the Chiral Magnetic Wave (CMW), causing a charge-dependent anisotropic flow. The charge dependence of the three-particle correlator γab, often employed as evidence for the CME, is measured in Xe–Xe collisions at sNN = 5.44 TeV. This correlator depends strongly on centrality and is similar to that in Pb–Pb collisions. This finding and the prediction of a significantly larger CME signal in Pb–Pb than Xe–Xe collisions from Monte Carlo calculations including amagnetic field due to spectators point to a large non-CME contribution to the correlator. Furthermore, it is reproduced by the Anomalous Viscous Fluid Dynamics model with values of the CME signal close to zero and by a blast wave model calculation that incorporates background effects. The charge dependence of elliptic (v2) and triangular (v3) flow coefficients of unidentified charged hadrons and pions are used to search for the CMW in Pb–Pb collisions atsNN = 5.02TeV. The v3 results are consistent with those of v2, which suggests a significant background contribution. *** Particles and Nuclei International Conference PANIC2021 *** *** 5 10 September, 2021 *** *** Online ***