Measurement of the branching fraction and time-dependent CP asymmetry for B0→J/ψπ0 decays

Le résumé fourni par la source

We measure the branching fraction and time-dependent $CP$-violating asymmetry for ${B}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{0}$ decays using a data sample of $711\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected on the $\mathrm{\ensuremath{\Upsilon}}(4S)$ resonance by the Belle experiment running at the KEKB ${e}^{+}{e}^{\ensuremath{-}}$ collider. The branching fraction is measured to be $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{0})=\phantom{\rule{0ex}{0ex}}[1.62\ifmmode\pm\else\textpm\fi{}0.11(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, which is the most precise measurement to date. The measured $CP$ asymmetry parameters are $\mathcal{S}=\ensuremath{-}0.59\ifmmode\pm\else\textpm\fi{}0.19(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{syst})$ and $\mathcal{A}=\ensuremath{-}0.15\ifmmode\pm\else\textpm\fi{}0.14(\mathrm{stat})\genfrac{}{}{0}{}{+0.04}{\ensuremath{-}0.03}(\mathrm{syst})$. The mixing-induced $CP$ asymmetry ($\mathcal{S}$) differs from the case of no $CP$ violation by 3.0 standard deviations, and the direct $CP$ asymmetry ($\mathcal{A}$) is consistent with zero.

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