Inclusive $J/\psi$ production at mid-rapidity in p-Pb collisions at $\sqrt{^{s}NN}$=5.02 TeV

Charmonia are a key observable for deconfinement in nucleus-nucleus (A-A) collisions at the LHC. Measurements in proton-nucleus (p-A) collisions and their comparison with proton-proton (pp) collision results provide complementary information on nuclear effects that are present in the absence of the Quark-Gluon Plasma (QGP). In addition, the calculation of the production of charmonia in p-A collisions presents a challenging test of perturbative QCD at low scales "Q^2" and low fractional momentum of the involved partons. The inclusive J/"\psi" production in proton-lead collisions at "\sqrt(s_{NN})= 5.02" TeV has been measured with ALICE in the "e^+e^-"decay channel at mid-rapidity down to vanishing transverse momentum ("p_T"): integrated, as a function of "p_T", centrality and charged-particle multiplicity. The nuclear modification factor of J/"\psi" indicates a strong suppression of charmonium production integrated, at low "p_T" and as function of centrality. The dependence of the normalised J/"\psi" yield as a function of the normalised charged particle multiplicity is consistent with the measurement in pp collisions and in the open heavy-flavour sector. It provides information on the correlation of soft and hard particle production. An extrapolation of the expected J/"\psi" production behaviour in A-A collisions based on the p-A measurement assuming the factorisation of the nuclear modi cation strengthens the evidence for an additional J/"\psi" production component at low "p_T" in A-A collisions. This component is expected from J/"\psi" production from unbound charm quarks within the QGP or at the phase boundary.