  The dilepton invariant mass spectrum measured in heavy-ion collisions
includes contributions from important QGP probes such as thermal radiation and
the quarkonium ($J/\psi$, $\psi'$ and $\Upsilon$) states. Dileptons coming from
hard $q \bar q$ scattering, the Drell-Yan process, contribute in all mass
regions. In heavy-ion colliders, such as the LHC, semileptonic decays of heavy
flavor hadrons provide a substantial contribution to the dilepton continuum.
The dilepton continuum can give quantitative information about heavy quark
yields and their modification in the medium and thus it is important to know
all different sources which populate the continuum.
  In the present study, we calculate $c \bar c$ and $b \bar b$ production and
determine their contributions to the dilepton continuum in Pb+Pb collisions at
$\sqrt{s_{_{NN}}} = 2.76$ TeV with and without including heavy quark energy
loss. We also calculate the rates for Drell-Yan and thermal dilepton
production. The contributions to the continuum from these dilepton sources are
studied in the kinematic ranges relevant for the LHC detectors. The relatively
high $p_T$ cutoff for single leptons excludes most dileptons produced by the
thermal medium. Heavy flavors are the dominant source of dilepton production in
all the kinematic regimes except at forward rapidities where Drell-Yan start
dominating in high mass range beyond 10 GeV/$c^2$.
