Measurement of the Branching Fraction For the Semileptonic Decay D0(+)→π−(0)μ+νμ and Test of Lepton Flavor Universality

Le résumé fourni par la source

Using a data sample corresponding to an integrated luminosity of $2.93\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ taken at a center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we perform an analysis of the semileptonic decays ${D}^{0(+)}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}(0)}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}$. The branching fractions of ${D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ and ${D}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ are measured to be $(0.272\ifmmode\pm\else\textpm\fi{}0.00{8}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.00{6}_{\mathrm{syst}})%$ and $(0.350\ifmmode\pm\else\textpm\fi{}0.01{1}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.01{0}_{\mathrm{syst}})%$, respectively, where the former is of much improved precision compared to previous results and the latter is determined for the first time. Using these results along with previous BESIII measurements of ${D}^{0(+)}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}(0)}{e}^{+}{\ensuremath{\nu}}_{e}$, we calculate the branching fraction ratios to be ${\mathcal{R}}^{0}\ensuremath{\equiv}{\mathcal{B}}_{{D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}}/{\mathcal{B}}_{{D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}{\ensuremath{\nu}}_{e}}=0.922\ifmmode\pm\else\textpm\fi{}0.03{0}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.02{2}_{\mathrm{syst}}$ and ${\mathcal{R}}^{+}\ensuremath{\equiv}{\mathcal{B}}_{{D}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}}/{\mathcal{B}}_{{D}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{e}^{+}{\ensuremath{\nu}}_{e}}=0.964\ifmmode\pm\else\textpm\fi{}0.03{7}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.02{6}_{\mathrm{syst}}$, which are compatible with the theoretical expectation of lepton flavor universality within $1.7\ensuremath{\sigma}$ and $0.5\ensuremath{\sigma}$, respectively. We also examine the branching fraction ratios in different four-momentum transfer square regions, and find no significant deviations from the standard model predictions.

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