Beam-Energy and System-Size Dependence of Dynamical Net Charge Fluctuations

Abstract

We present measurements of net charge fluctuations in $Au _s16 Au$ collisions at $sqrt{s_{NN}} = $ 19.6, 62.4, 130, and 200 GeV, $Cu _s16 Cu$ collisions at $sqrt{s_{NN}} = $ 62.4, 200 GeV, and $p _s16 p$ collisions at $sqrt{s} = $ 200 GeV using the dynamical net charge fluctuations measure $nu_{_s16-{rm,dyn}}$. We observe that the dynamical fluctuations are non-zero at all energies and exhibit a modest dependence on beam energy. A weak system size dependence is also observed. We examine the collision centrality dependence of the net charge fluctuations and find that dynamical net charge fluctuations violate $1/N_{ch}$ scaling, but display approximate $1/N_{part}$ scaling. We also study the azimuthal and rapidity dependence of the net charge correlation strength and observe strong dependence on the azimuthal angular range and pseudorapidity widths integrated to measure the correlation.