  A Monte Carlo model, initially developed for soft pp and AA collisions at
high energy, is applied for proton-lead interaction at the LHC energy.
Elementary collisions are implemented at the partonic level and do not involve
the usual Glauber supposition of independent nucleon-nucleon collisions. The
average number of participating nucleons and charged multiplicity in p-Pb
collisions were calculated and compared with the predictions of Glauber model
and experimental data. It was demonstrated that taking into account the energy
conservation results in the number of participating nucleons considerably lower
than in the Glauber approach. Different ways of centrality determination in pA
are discussed and the influence of the methods of centrality definition on mean
observables and their variances is studied.

High Energy Physics - Phenomenology;Nuclear Theory