Multiplicity evolution of identified particle charge-dependent correlations in Pb-Pb, p-Pb and pp collisions at the LHC with ALICE

The charge pair creation and transport processes in heavy-ion collisions are investigated experimentally by measurements of charge-dependent correlations of identified particle pairs, related to the Balance Function[1]. The produced pair separation in rapidity is expected to be larger for hadrons arising from quark-antiquark pair creation in the early stages of the collision than for hadrons emerging from the later hadronization stage. Correlations are reported for charged-pion pairs in Pb-Pb, p-Pb and pp collisions at $\surd $s$_{\mathrm{NN}}=$2.76, 5.02 and 7 TeV, respectively; and for charged-kaon pairs in Pb-Pb collisions at $\surd $s$_{\mathrm{NN}}=$2.76 TeV. The correlations are measured as a function of relative rapidity $\Delta $y and azimuthal angle $\Delta \phi $, and are dominated by a peak centered at $\Delta $y$=\Delta \phi =$0. We observe that the peak widths in $\Delta $y and $\Delta \phi $ are narrower in higher multiplicity events in Pb-Pb, p-Pb, and pp collisions, which is consistent with the effects of radial flow, as well as the two-wave quark production mechanism. We investigate the charge transport and system evolution further by studying the $\Delta \phi $ width of the peak as a function of $\Delta $y. [1]Pratt,PRC85(2012)014904