  A measurement of the t t-bar production cross section at sqrt(s) = 13 TeV is
presented using proton-proton collisions, corresponding to an integrated
luminosity of 2.2 inverse femtobarns, collected with the CMS detector at the
LHC. Final states with one isolated charged lepton (electron or muon) and at
least one jet are selected and categorized according to the accompanying jet
multiplicity. From a likelihood fit to the invariant mass distribution of the
isolated lepton and a jet identified as coming from the hadronization of a
bottom quark, the cross section is measured to be sigma(t t-bar) = 888 +/- 2
(stat) +26 -28 (syst) +/- 20 (lumi) pb, in agreement with the standard model
prediction. Using the expected dependence of the cross section on the pole mass
of the top quark (m[t]), the value of m[t] is found to be 170.6 +/- 2.7 GeV.
