Ridges and Soft Jet Components in Untriggered Di-hadron Correlations in Pb+Pb Collisions at 2.76 TeV

Abstract

We study untriggered di-hadron correlations in Pb+Pb at 2.76 TeV, based on an event-by-event simulation of a hydrodynamic expansion starting from flux tube initial conditions. The correlation function shows interesting structures as a function of the pseudorapidity difference $\Delta\eta$ and the azimuthal angle difference $\Delta\phi$, in particular comparing different centralities. We can clearly identify a peak-like nearside structure associated with very low momentum components of jets for peripheral collisions, which disappears towards central collisions. On the other hand, a very broad ridge structure from asymmetric flow seen at central collisions, gets smaller and finally disappears towards peripheral collisions.