The product of the electronic width of the $psi(2S)$ meson and the branching fraction of its decay to the muon pair was measured in the $e^{+}e^{-} to psi(2S) to mu^{+}mu^{-}$ process using nine data sets corresponding to an integrated luminosity of about 6.5 pb$^{-1}$ collected with the KEDR detector at the VEPP-4M electron-positron collider: [ Gamma_{ee}timesmathcal{B}_{mumu} = 19.3 pm 0.3 pm 0.5 ~text{eV}. ] Adding the previous KEDR results on hadronic and leptonic channels, the values of the $psi(2S)$ electronic width were obtained under two assumptions: either with the assumption of lepton universality [ Gamma_{ee} = 2.279 pm 0.015 pm 0.042 ~text{keV} ] or without it, summing up hadronic and three independent leptonic channels: [ Gamma_{ee} = 2.282 pm 0.015 pm 0.042 ~text{keV}. ]
تحميل البحث