Axial-Vector D_{1} Hadrons in D^{*}π Scattering from QCD

We present I=1/2 D^{*}π scattering amplitudes from lattice QCD and determine two low-lying J^{P}=1^{+} axial-vector D_{1} states and a J^{P}=2^{+} tensor D_{2}^{*}. Computing finite-volume spectra at a light-quark mass corresponding to m_{π}≈391  MeV, for the first time, we are able to constrain coupled J^{P}=1^{+} D^{*}π amplitudes with ^{2S+1}ℓ_{J}=^{3}S_{1} and ^{3}D_{1} as well as coupled J^{P}=2^{+}  Dπ(^{1}D_{2}} and D^{*}π(^{3}D_{2}} amplitudes via Lüscher's quantization condition. Analyzing the scattering amplitudes for poles we find a near-threshold bound state, producing a broad feature in D^{*}π{^{3}S_{1}}. A narrow bump occurs in D^{*}π{^{3}D_{1}} due to a D_{1} resonance. A single resonance is found in J^{P}=2^{+} coupled to Dπ and D^{*}π. A relatively low mass and large coupling are found for the lightest D_{1}, suggestive of a state that will evolve into a broad resonance as the light-quark mass is reduced. An earlier calculation of the scalar D_{0}^{*} using the same light-quark mass enables comparisons to the heavy-quark limit.