  Prediction of $Z\rightarrow l^{+}l^{-}$ production cross section (where
$l^{\pm} =e^{\pm},\mu^{\pm}$) in proton-proton collisions at $\sqrt{s}$=14 TeV
is estimated up to next-to-next-to-leading order (NNLO) in perturbative QCD
including next-to-leading order (NLO) electroweak (EW) corrections. The total
inclusive Z boson production cross section times leptonic branching ratio,
within the invariant mass window $66<m_{ll}<116$ GeV, is predicted using NNLO
HERAPDF2.0 at NNLO QCD and NLO EW as $\sigma_{Z}^{Tot}$=
2111.69$_{-26.92}^{+26.31}$ (PDF) $\pm11$ ($\alpha_{s}$) $\pm$17 (scale)
$^{+57.41}_{-30.98}$ (parameterization and model). Theoretical prediction of
the fiducial cross section is further computed with the latest modern PDF
models (CT14, MMHT2014, NNPDF3.0, HERAPDF2.0 and ABM12) at NNLO for QCD and NLO
for EW. The central values of the predictions are based on DYNNLO 1.5 program
and the uncertainties are extracted using FEWZ 3.1 program. In addition, the
cross section is also calculated as functions of $\mu_{R}$ and $\mu_{F}$
scales. The choice of $\mu_{R}$ and $\mu_{F}$ for scale variation uncertainty
is further discussed in details.
