Analysis of D⁺→K^-π⁺e ⁺νe and D⁺→K ^-π⁺μ⁺+νμ semileptonic decays

Using a large sample (≈11800 events) of D⁺→K ^-π⁺e⁺νe and D⁺→K ^-π⁺μ⁺νμ decays collected by the CLEO-c detector running at the ψ(3770), we measure the helicity basis form factors free from the assumptions of spectroscopic pole dominance and provide new, accurate measurements of the absolute branching fractions for D ⁺→K^̄*0e⁺νe and D⁺→K^̄*0μ⁺νμ decays. We find branching fractions which are consistent with previous world averages. Our measured helicity basis form factors are consistent with the spectroscopic pole dominance predictions for the three main helicity basis form factors describing D⁺→K^̄*0 ⁺ν decay. The ability to analyze D⁺→K ^-π⁺μ⁺νμ allows us to make the first nonparametric measurements of the mass-suppressed form factor. Our result is inconsistent with existing lattice QCD calculations. Finally, we measure the form factor that controls nonresonant s-wave interference with the D ⁺→K^̄*0⁺ν amplitude and search for evidence of possible additional nonresonant d- or f-wave interference with the K^̄*0.