We combine measurements of the top quark pair production cross section in p (p) over bar collisions in the l jets, ll, and tau l final states ( where l is an electron or muon) at a center of mass energy of root s = 1.96 TeV in 1 fb(-1) of data collected with the D0 detector. For a top quark mass of 170 GeV/c(2), we obtain sigma(t (t) over bar) = 8.18(-0.87)( 0.98) pb in agreement with the theoretical prediction.
Based on predictions from higher order quantum chromodynamics, we extract a mass for the top quark from the combined t (t) over bar cross section, consistent with the world average of the top quark mass. In addition, the ratios of t (t) over bar cross sections in different final states are used to set upper limits on the branching fractions B(t -} H( )b -} tau( ) vb) and B(t -} H( )b -} c (s) over barb) as a function of the charged Higgs boson mass.