  Detailed studies have been carried out on the impact of the LHC top quark
pair production data on gluon PDF, in the context of the CTEQ-TEA global PDF
fit, with the ePump-updating method. The considered $t\bar{t}$ data include
single differential distributions from ATLAS and double differential
distributions from CMS, both at 8 TeV. All analyses have been carried out at
the NNLO, using fastNNLO tables. We show that the sensitivity per data point of
the LHC $t\bar{t}$ data is similar to that of jet data, as included in the
CT14HERA2 fit, while the total sensitivity of the present $t\bar{t}$ data is
not as large as the jet data because of the much smaller number of $t\bar{t}$
data points in the presently available data.
