  We study the mass dependence for identified-particle average transverse
momentum and harmonic flow coefficients in proton-lead (p-Pb) collisions,
recently measured at the LHC. The collective mechanism in the p-Pb system
predicts a specific mass ordering in these observables: the growth of the
average transverse momentum with the particle mass and a mass splitting of the
elliptic flow coefficient, i.e., smaller differential elliptic flow of protons
than pions for p_T<2 GeV. This provides an opportunity to distinguish between
the collective scenario and the mechanism based on the initial gluon dynamics
in the evolution of the p-Pb system.
