Role of nuclear gluon distribution on particle production in heavy ion collisions

The transverse momentum spectra of hadrons is calculated from the unintegrated gluon distribution (UGD) within the $k_T$-factorization framework at small $x$. Starting from $pp$ collisions, the modification caused by the nuclear medium is incorporated in the UGD at high energies, which is related to the nuclear shadowing phenomenon. Moreover, we consider that particle production from minijet decaying is not enough to explain the $p_T$ spectra in $AA$ collisions due to collective phenomena that take place after the hard collision. The Boltzmann-Gibbs Blast Wave (BGBW) distribution is utilized in order to evaluate the distribution of particle production in equilibrium. Data from ALICE collaboration for $PbPb$ collisions at $\sqrt{s}=2.76$ TeV are analyzed and the nuclear modification factor for pion production is computed.