Fluctuations of the azimuthal particle distribution in NA49 at the CERN SPS

Abstract

Event-by-event fluctuations and correlations in azimuthal angle are currently widely investigated in various experiments. In this paper the $\Phi$ measure (earlier used in experiments to evaluate fluctuations in transverse momentum) is now applied to azimuthal angle $\phi$. Properties of this $\Phi_{\phi}$ function are investigated through fast generators and with complex models such as Pythia, Hijing, and UrQMD. Preliminary results of NA49 on $\Phi_{\phi}$ are also presented. The system size dependence (p+p, C+C, Si+Si and 6 centralities of Pb+Pb) at the highest SPS energy (158$A$ GeV) is shown, as well as the energy dependence (20$A$ - 158$A$ GeV) for the 7.2\% most central Pb+Pb interactions.