Experimental transverse momentum spectra of identified particles in p-Pb collisions at 5.02 TeV show many similarities to the corresponding Pb-Pb results, the latter ones usually being interpreted in term of hydrodynamic flow. We analyse these data using EPOS3, an event generator based on a 3D+1 viscous hydrodynamical evolution starting from flux tube initial conditions, which are generated in the Gribov-Regge multiple scattering framework. An individual scattering is referred to as Pomeron, identified with a parton ladder, eventually showing up as flux tubes (or strings). Each parton ladder is composed of a pQCD hard process, plus initial and final state linear parton emission. Nonlinear effects are considered by using saturation scales Qs, depending on the energy and the number of participants connected to the Pomeron in question. We compute transverse momentum (pt) spectra of pions, kaons, protons, lambdas, and Ξ baryons in p-Pb and p-p scattering, compared to experimental data and many other models. In this way we show in a quantitative fashion that p-Pb data (and even p-p ones) show the typical "flow effect" of enhanced particle production at intermediate pt values, more and more visible with increasing hadron mass.

We show that a fluid dynamical scenario describes quantitatively the observed mass splitting of the elliptical flow coefficients v2 for pions, kaons, and protons. This provides a strong argument in favor of the existence of a fluid dynamical expansion in pPb collisions at 5TeV.One of the strongest signals of collective flow in heavy ion collisions is the fact that the transverse momentum dependence of the elliptical flow coefficient v 2 (measuring the azimuthal asymmetry) depends in a very characteristic way on the mass of the observed hadrons. This has been predicted [1] and impressively confirmed experimentally later [2,3]. Can we also "prove" the existence of flow in small systems like proton-lead collisions, where such a collective behavior has not been expected?Information about flow asymmetries can be obtained via studying two particle correlations as a function of the pseudorapidity difference ∆η and the azimuthal angle difference ∆φ. So-called ridge structures (very broad in ∆η) have been observed first in heavy ion collisions, later also in pp [4] and very recently in pPb collisions [5][6][7]. In case of heavy ions, these structures appear naturally in models employing a hydrodynamic expansion, in an event-by-event treatment.To clearly pin down the origin of such structures in small systems, one needs to consider identified particles. In the fluid dynamical scenario, where particles are produced in the local rest frame of fluid cells characterized by transverse velocities, large mass particles (compared to low mass ones) are pushed to higher transverse momenta, visible in p t distributions, but also in the dihadron correlations. Both effects are clearly seen in experimental data. In this paper, we focus on dihadron correlations and the v 2 coefficients.The following discussion is based on ALICE results on dihadron correlations [5, 8] and EPOS3 simulations. EPOS3 is a major update of the work described in [11] (EPOS2). Here, we introduced a theoretical scheme which accounts for hydrodynamically expanding bulk matter, jets, and the interaction between the two. The whole transverse momentum range is covered, from very low to very high p t . In [11], we show that this approach can accommodate spectra of jets with p t up to 200 GeV/c in pp scattering at 7 TeV, as well as particle yields and harmonic flows with p t between 0 and 20 GeV/c in PbPb collisions at 2.76 TeV. To our knowledge, this is the only model able to describe the famous lambda to kaon enhancement correctly over the whole p t range. New features of EPOS3 are: an event-by-event 3D+1 viscous hydrodynamical evolution, and a new treatment of high parton densities, via an individual parton saturation scale Q s for each elementary scattering. More details will be given in the appendix. All results in this paper are based on EPOS3.074.As in [11], the basis of our approach is multiple scattering (even for pp), where a single scattering is a hard elementary scattering plus initial state radiation, the whole object being referred to as parton ladder or...