  Despite no new physics so far at the LHC, a $Z'$ boson with $m_{Z'} \sim 100$
GeV could still emerge via Drell-Yan (DY) production, $q \bar q \to Z' \to
\mu^+ \mu^-$, in the next few years. To unravel the nature of the $Z'$
coupling, we utilize the $c$- and $b$-tagging algorithms developed by ATLAS and
CMS to investigate $cg \to c Z'$ at 14 TeV LHC. While light-jet contamination
can be eliminated, mistagged $b$-jets cannot be rejected in any of the tagging
schemes we adopt. On the other hand, for nonzero $bbZ'$ coupling, far superior
$b$-tagging could discover the $bg \to b Z'$ process, where again light-jet
mistag can be ruled out, but mistagged $c$-jets cannot yet be excluded.
Provided that DY production is discovered soon enough, we find that a
simultaneous search for $c g \to c Z'$ and $b g \to b Z'$ can conclusively
discern the nature of $Z'$ couplings involved.
