Study of the decay D0 →ρ (770)-e+νe

We present a study of the semileptonic decay D0→π-π0e+νe using an e+e- annihilation data sample of 7.93 fb-1 collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The branching fraction of D0→ρ(770)-e+νe is measured to be (1.439±0.033(stat)±0.027(syst))×10-3, which is a factor 1.6 more precise than previous measurements. By performing an amplitude analysis, we measure the hadronic form-factor ratios of D0→ρ(770)-e+νe at q2=0 assuming the single-pole-dominance parametrization: rV=V(0)/A1(0)=1.548±0.079(stat)±0.041(syst) and r2=A2(0)/A1(0)=0.823±0.056(stat)±0.026(syst).