p+Pb collisions at LHC are precious mainly for disentagling initial and final state effects in heavy in collisions. One of the basic measurments is transverse momentum distribution for different particle species in order to confront them with those of pp and PbPb collisions. One of the great surprises was that high multiplicity pPb events start to show up some collectivity effects while for low multiplicities they do not differ much from the elementary (i.e. pp ) colisions. These results can be confronted with different QCD inspired models in order to test different posiible mechanisms explaining these properties. Also in case of the nuclear modification factor the same coclusions can be drawn. The nature of this observed collectivity is actually strongle debated.  

From our point of view, of the cosmic rays of ultra high energy, the transverse momentum is key to develop trustable hadronic interaction models and codes to simulate our analysis.