Abstract
By analyzing a 2.93 fb^{-1} data sample of e^{+}e^{-} collisions, recorded at a center-of-mass energy of 3.773GeV with the BESIII detector operated at the BEPCII collider, we report the first observation of the semileptonic D^{+} transition into the axial-vector meson D^{+}→K[over ¯]_{1}(1270)^{0}e^{+}ν_{e} with a statistical significance greater than 10σ. Its decay branching fraction is determined to be B[D^{+}→K[over ¯]_{1}(1270)^{0}e^{+}ν_{e}]=(2.30±0.26_{-0.21}^{+0.18}±0.25)×10^{-3}, where the first and second uncertainties are statistical and systematic, respectively, and the third originates from the input branching fraction of K[over ¯]_{1}(1270)^{0}→K^{-}π^{+}π^{0}.
Highlights
with the BESIII detector operated at the BEPCII collider
we report the first observation of the semileptonic Dþ transition into the axial-vector meson Dþ
Those transitions into S-wave states have been extensively studied in theory and experiment
Summary
By analyzing a 2.93 fb−1 data sample of eþe− collisions, recorded at a center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we report the first observation of the semileptonic Dþ transition into the axial-vector meson Dþ → K 1ð1270Þ0eþνe with a statistical significance greater than 10σ. The physical mass eigenstates of the strange axial-vector mesons, K1ð1270Þ and K1ð1400Þ, are mixtures of the 1P1 and 3P1 states with a mixing angle θK1. These mesons have been thoroughly studied via τ, B, D, ψð3686Þ, and J=ψ decays, as well as via Kp scattering [3–12].
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