Improved measurement of the absolute branching fraction of inclusive semileptonic ?c plus decay

Using 4.5 fb-1 of e+e- annihilation data samples collected at center-of-mass energies ranging from 4.600 to 4.698 GeV with the BESIII detector at the BEPCII collider, we measured the absolute branching fraction for the inclusive semileptonic decay A+c -Xe+ve, where X refers to any possible particle system. The branching fraction of the decay is determined to be B(A+c -Xe+ve) = (4.06 +/- 0.10stat +/- 0.09syst)%. Our result improves the precision of previous measurements of B(A+c -Xe+ve) by more than threefold. Using the known A+c lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons, we measure the ratio of inclusive semileptonic decay widths Gamma(A+c -Xe+ve)/Gamma over bar (D -Xe+ve) = 1.28 +/- 0.05, where statistical and systematic uncertainties are combined.