Reaction centrality & scaling of baseline p+p,p+A observables

• Determination of the properties of the hot strongly interacting medium formed in A+A collisions requires comparing to:

  • No medium data : p+p collisions
  • Cold medium data: p+A collisions

• Usual particle production observables in p+p,A reactions scale according to:

  • The number of participant ("wounded") nucleons Npart : for "soft" processes
  • The number of binary nucleon collisions Ncolls : for "hard" processes

• Ncolls & Npart are directly related to the centrality of the reaction through: Glauber geometrical model + Global Detectors (ZDC,BBC) response