Measurement of the D*(2010)⁺ –D⁺ Mass Difference

We measure the mass difference, Δm₊, between the D*(2010)⁺ and the D⁺ using the decay chain D*(2010)⁺ → D⁺π⁰ with D⁺ → K⁻π⁺π⁺. The data were recorded with the BABAR detector at center-of-mass energies at and near the Υ(4S) resonance, and correspond to an integrated luminosity of approximately 468 fb⁻¹. We measure Δm₊ = (140 601.0 ± 6.8 [stat] ± 12.9 [syst]) keV. We combine this result with a previous BABAR measurement of Δm₀ ≡ m(D*(2010)⁺) - m(D⁰) to obtain Δm_D = m(D⁺) - m(D⁰) = (4824.9 ± 6.8 [stat] ± 12.9 [syst]) keV. These results are compatible with and approximately five times more precise than the Particle Data Group averages.