Determination of the absolute branching fractions of D⁰ → K⁻e⁺ν_e and D⁺→¯K⁰e⁺ν_e

Using 2.93  fb−1 of e+e− collision data collected with the BESIII detector at a center-of-mass energy of 3.773 GeV, we measure the absolute branching fractions of the decays D0→K−e+νe and D+→¯K0e+νe to be (3.567±0.031stat±0.025syst)% and (8.68±0.14stat±0.16syst)%, respectively. Starting with the process e+e−→D¯D, a new reconstruction method is employed to select events that contain candidates for both D→¯Ke+νe and ¯D→Ke−¯νe decays. The branching fractions reported in this work are consistent within uncertainties with previous BESIII measurements that selected events containing D→¯Ke+νe and hadronic ¯D decays. Combining our results with the lifetimes of the D0 and D+ mesons and the previous BESIII measurements leads to a ratio of the two decay partial widths of ¯ΓD0→K−e+νe¯ΓD+→¯K0e+νe=1.039±0.021. This ratio supports isospin symmetry in the D0→K−e+νe and D+→¯K0e+νe decays within 1.9σ.