Multiplicity dependence of identified particle production in PP collisions with ALICE

On behalf of the ALICE Collaboration A comprehensive measurement of the multiplicity dependence of identified particle production in proton-proton (pp) collisions is important for the understanding of small and large colliding systems. The transverse momentum (pT) dependence of particle ratios and the integrated yield ratio of various particles such as π, K, K 0 S , K * 0 , p, Λ, Ξ, Ω in pp collisions at 7 TeV are reported. The measurements are also compared with the results obtained in proton-lead (p–Pb) and lead-lead (Pb–Pb) collisions at √ s NN = 5.02 TeV and 2.76 TeV, respectively. The production of strange and multi-strange hadrons in pp collisions exhibits a significant increase with the average charged particle multiplicity similar to the increase observed in p-Pb collisions. None of the common QCD-inspired models (DIPSY, EPOS, PYTHIA8) are able to simultaneously describe the observed multiplicity dependent particle ratios.