Study of the $pp \to Z jets \to \mu^{+}\mu^{-}$ + jets channel with the CMS detector at LHC

A study of the pp -> Z + n jets -> mu+mu- + n jets processes, with n > 0 is performed on an MC generated data sample. Signal selection criteria are given and an original background subtraction procedure is applied. A measurement of the pp -> Z + n jets -> mu+mu- + n jets cross section is made for the channels with n = 1, 2, 3, jets. A correspondance criteria is established between the number of jets observed and the number of partons with high transverse momentum produced in the hard pp scattering. A measurement is made of the hard pp -> Z + n partons processes' cross sections, with n = 1, 2, 3.