Investigation of possible hadronic flow insNN=5.02TeVp−Pbcollisions

Abstract

Using the ultrarelativistic quantum molecular dynamics (UrQMD) model, we investigate azimuthal correlations in $p\ensuremath{-}\mathrm{Pb}$ collisions at $\sqrt{{s}_{\mathit{NN}}}=5.02\phantom{\rule{0.28em}{0ex}}\mathrm{TeV}$. Comparison with the experimental data shows that UrQMD cannot reproduce the multiplicity dependence of two- and four-particle cumulants, especially the transition from positive to negative values of ${c}_{2}{4}$ in high-multiplicity events, which has been taken as experimental evidence of collectivity in $p\ensuremath{-}\mathrm{Pb}$ collisions. Meanwhile, UrQMD cannot describe the differential elliptic flow ${v}_{2}({p}_{\mathrm{T}})$ of all charged hadrons at various multiplicity classes. These discrepancies show that the simulated hadronic $p\ensuremath{-}\mathrm{Pb}$ systems cannot generate enough collective flow as observed in experiment, the associated hadron emissions are largely influenced by nonflow effects. However, the characteristic ${v}_{2}({p}_{\mathrm{T}})$ mass ordering of pions, kaons, and protons is observed in UrQMD, which is the consequence of hadronic interactions and not necessarily associated with strong fluid-like expansions.