  The inclusive cross section for top quark pair production is measured in
proton-proton collisions at sqrt(s) = 7 and 8 TeV, corresponding to 5.0 and
19.7 invers-femtobarns, respectively, with the CMS experiment at the LHC. The
cross sections are measured in the electron-muon channel using a binned
likelihood fit to multi-differential final state distributions related to
identified b quark jets and other jets in the event. The measured cross section
values are 173.6 +/- 2.1 (stat) +4.5-4.0 (syst) +/- 3.8 (lumi) pb at sqrt(s) =
7 TeV, and 244.9 +/- 1.4 (stat) +6.3-5.5 (syst) +/- 6.4 (lumi) pb at sqrt(s) =
8 TeV, in good agreement with QCD calculations at next-to-next-to-leading-order
accuracy. The ratio of the cross sections measured at 7 and 8 TeV is
determined, as well as cross sections in the fiducial regions defined by the
acceptance requirements on the two charged leptons in the final state. The
cross section results are used to determine the top quark pole mass via the
dependence of the theoretically predicted cross section on the mass, giving a
best result of 173.8 +1.7-1.8 GeV. The data at sqrt(s) = 8 TeV are also used to
set limits, for two neutralino mass values, on the pair production of
supersymmetric top squarks with masses close to the top quark mass.
