  Recently there has been a huge interest in the diphoton excess around 750 GeV
reported by both ATLAS and CMS collaborations, although the newest analysis
with more statistics does not seem to support the excess. Nevertheless, the
diphoton channel at the LHC experiments are a powerful tool to probe a new
physics. One of the most natural explanations of a diphoton excess, if it
occurs, could be a new scalar boson with exotic colored particles. In this
setup, it would be legitimate to ask what is the role of this new scalar in
nature. A heavy neutral gauge boson ($Z'$) is one of the traditional targets of
the discovery at the collider experiments with numerous motivations. While the
Landau-Yang theorem dictates the diphoton excess cannot be this spin-1 gauge
boson, there is a strong correlation of a new heavy gauge boson and a new
scalar boson which provides a mass to the gauge boson being at the same mass
scale. In this paper, we point out a simple fact that a new scalar with a
property similar to the recently highlighted 750 GeV would suggest an existence
of a TeV scale $Z'$ gauge boson that might be within the reach of the LHC Run 2
experiments. We take a scenario of the well-motivated and popular gauged $B-L$
symmetry and require the gauge coupling unification to predict the mass and
other properties of the $Z'$ and illustrate the discovery of the $Z'$ would
occur during the LHC experiments.
