Observation of Υ(4S) Decays to π+π−Υ(1S) and π+π−Υ(2S)

Le résumé fourni par la source

We present the first measurement of $\ensuremath{\Upsilon}(4S)$ decays to ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\Upsilon}(1S)$ and ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\Upsilon}(2S)$ based on a sample of $230\ifmmode\times\else\texttimes\fi{}{10}^{6}\ensuremath{\Upsilon}(4S)$ mesons collected with the BABAR detector. We measure the product branching fractions $\mathcal{B}\mathbf{(}\ensuremath{\Upsilon}(4S)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\Upsilon}(1S)\mathbf{)}\ifmmode\times\else\texttimes\fi{}\mathcal{B}\mathbf{(}\ensuremath{\Upsilon}(1S)\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}\mathbf{)}=(2.23\ifmmode\pm\else\textpm\fi{}{0.25}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.27}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $\mathcal{B}\mathbf{(}\ensuremath{\Upsilon}(4S)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\Upsilon}(2S)\mathbf{)}\ifmmode\times\else\texttimes\fi{}\mathcal{B}\mathbf{(}\ensuremath{\Upsilon}(2S)\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}\mathbf{)}=(1.69\ifmmode\pm\else\textpm\fi{}{0.26}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.20}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, from which we derive the partial widths $\ensuremath{\Gamma}\mathbf{(}\ensuremath{\Upsilon}(4S)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\Upsilon}(1S)\mathbf{)}=(1.8\ifmmode\pm\else\textpm\fi{}0.4)\text{ }\text{ }\mathrm{keV}$ and $\ensuremath{\Gamma}\mathbf{(}\ensuremath{\Upsilon}(4S)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\Upsilon}(2S)\mathbf{)}=(2.7\ifmmode\pm\else\textpm\fi{}0.8)\text{ }\text{ }\mathrm{keV}$.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.