  In this work, we calculate energy loss of heavy quark (charm and bottom) due
to elastic collisions and gluon radiation in hot/dense medium. The collisional
energy loss has been obtained using QCD calculations. The radiative energy loss
is calculated using reaction operator formalism and generalized dead cone
approach. We rederive the energy loss expression using same assumptions as
generalized dead cone approach but obtain slightly different results. We also
improve the model employed to calculate path length and the system evolution.
The nuclear modification factors $R_{AA}$ including shadowing and energy loss
are evaluated for $B$ and $D$ mesons and are compared with the measurements in
PbPb collision at $\sqrt{s_{NN}}$ = 2.76 TeV and with the D meson and Heavy
flavour (HF) electrons measurements in AuAu collision at $\sqrt{s_{NN}}$ = 200
GeV. The radiative energy loss calculated by reaction operator formalism added
with collisional energy loss describes the RHIC HF electron suppression in high
$p_{T}$ range. It also describes the LHC measurement of $B$ meson suppression
but overestimates the suppression of $D$ meson. The radiative energy loss from
generalized dead cone approach describes the charm suppression at both RHIC as
well as LHC energies and requires energy loss due to collisions to be added in
order to describe the bottom suppression at LHC.
