Flow in pPb collisions? Further examination using φ(1020) - hadron correlation analysis.

The observation of long range azimuthal correlations in high multiplicity pp and pPb collisions measured at LHC was rather unexpected, and opened up new frontiers in studying high density QCD phenomena [1] [2] [3]. One of the striking features of these recent results is that it seems that different types of collisions like pp, pPb and PbPb start to share similar features when one investigates events in which high number of particles are produced. Although several theoretical models exist (e.g. CGC - Color Glass Condensate, hydrodynamic flow, jet induced ridge etc.), it cannot be determined from the experimental data collected up till today which one of them describes the true underlying physics of the collisions [4]. Also since the theories which describe these phenomena usually contain some parameters that can be fine tuned to agree with the experimental data, we can only resort to the basic scientific method of falsification, where we discard the model if it cannot account for experimental results.