  The parton distribution functions (PDFs) of the proton are one of the
essential ingredients to describe physics processes at hadron colliders. The Z
boson production data at the LHC have a potential to constrain PDFs, especially
the gluon distribution. In this study the CMS measurement of the inclusive
double differential Z boson production cross section in terms of transverse
momentum and rapidity are compared to the next-to-leading order theory
predictions at the center-of-mass energy of sqrt(s)=8 TeV with an integrated
luminosity of 19.71 inverse femtobarns. In addition, the sensitivity of this
measurement to PDFs is studied within the framework of the HERAFitter. A
moderate improvement to the gluon distribution is observed at the Bjorken x ~
0.1 region. However, in order to obtain further improvement to the gluon
distribution in the global fits, the higher-order theory calculations
accessible via fast techniques are necessary.
