Observation of the Semileptonic D+ Decay into the K¯1(1270)0 Axial-Vector Meson

Le résumé fourni par la source

By analyzing a $2.93\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ data sample of ${e}^{+}{e}^{\ensuremath{-}}$ 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 ${D}^{+}$ transition into the axial-vector meson ${D}^{+}\ensuremath{\rightarrow}{\overline{K}}_{1}(1270{)}^{0}{e}^{+}{\ensuremath{\nu}}_{e}$ with a statistical significance greater than $10\ensuremath{\sigma}$. Its decay branching fraction is determined to be $\mathcal{B}[{D}^{+}\ensuremath{\rightarrow}{\overline{K}}_{1}(1270{)}^{0}{e}^{+}{\ensuremath{\nu}}_{e}]=\phantom{\rule{0ex}{0ex}}(2.30\ifmmode\pm\else\textpm\fi{}{0.26}_{\ensuremath{-}0.21}^{+0.18}\ifmmode\pm\else\textpm\fi{}0.25)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, where the first and second uncertainties are statistical and systematic, respectively, and the third originates from the input branching fraction of ${\overline{K}}_{1}(1270{)}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}$.

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