We have calculated the nuclear modification factor ($R_{AA}$) of D and B mesons by considering the energy gain due to field fluctuations along with collisional and radiative energy loss of charm and beauty quarks in the hot and dense deconfined medium of quarks and gluons created in relativistic heavy ion collisions. We find a good agreement with the experimentally measured $R_{AA}$ of D and B mesons by ALICE and CMS experiments at $\sqrt {s_{NN}} = 2.76 $ TeV and $\sqrt {s_{NN}} = 5.02 $ TeV.