Measurement of e⁺ e^- → DD cross sections at the ψ(3770) resonance

We report new measurements of the cross sections for the production of DD final states at the ψ(3770) resonance. Our data sample consists of an integrated luminosity of 2.93 fb^-1 of e⁺e^- annihilation data produced by the BEPCII collider and collected and analyzed with the BESIII detector. We exclusively reconstruct three D⁰ and six D⁺ hadronic decay modes and use the ratio of the yield of fully reconstructed DD events ("double tags") to the yield of all reconstructed D or D mesons ("single tags") to determine the number of D⁰D⁰ and D⁺D^- events, benefiting from the cancellation of many systematic uncertainties. Combining these yields with an independent determination of the integrated luminosity of the data sample, we find the cross sections to be σ(e⁺e^- → D⁰D⁰) nb and σ(e⁺e^- → D⁺D^-) = (2.830 ±'> 0.011 ±> 0.026) nb, where the uncertainties are statistical and systematic, respectively.