Charmonium spectroscopy from inclusive ψ’ and<i>J/ψ</i>radiative decays

Abstract

Results from a detailed study using the Crystal Ball detector at the SLAC ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ storage ring SPEAR of the inclusive photon spectra from 1.8\ifmmode\times\else\texttimes\fi{}${10}^{6}$ \ensuremath{\psi}' and 2.2\ifmmode\times\else\texttimes\fi{}${10}^{6}$ J/\ensuremath{\psi} decays are presented. Radiative transitions from the \ensuremath{\psi}' to the ${\ensuremath{\chi}}_{2}$,1,0 states are observed with photon energies of 126.0\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\pm\else\textpm\fi{}4, 169.6\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}4, and 258.4\ifmmode\pm\else\textpm\fi{}0.4\ifmmode\pm\else\textpm\fi{}4 MeV and branching ratios B(\ensuremath{\psi}'\ensuremath{\rightarrow}\ensuremath{\gamma}${\ensuremath{\chi}}_{2}$,1,0) =(8.0\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.7)%, (9.0\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.7)%, and (9.9\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.8)%, respectively. Values for the natural linewidths of the \ensuremath{\chi} states are obtained: \ensuremath{\Gamma}(${\ensuremath{\chi}}_{2}$,1,0)=0.8--4.9, &lt;3.8, and 13--21 MeV, respectively (90% C.L.). Improved values are found for the branching ratios B(\ensuremath{\psi}'\ensuremath{\rightarrow}\ensuremath{\gamma}${\ensuremath{\eta}}_{c}$) =(0.28\ifmmode\pm\else\textpm\fi{}0.06)% and B(J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}${\ensuremath{\eta}}_{c}$)=(1.27\ifmmode\pm\else\textpm\fi{}0.36)%, and for the natural width \ensuremath{\Gamma}(${\ensuremath{\eta}}_{c}$)=11.5\ifmmode\pm\else\textpm\fi{}4.5 MeV.