Measurements of the Mass and Width of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>η</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math>Meson and of an<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>η</mml:mi><mml:mi>c</mml:mi></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:mn>2</mml:mn><mml:mi>S</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:math>Candidate

The mass ${m}_{{\ensuremath{\eta}}_{c}}$ and total width ${\ensuremath{\Gamma}}_{\mathrm{tot}}^{{\ensuremath{\eta}}_{c}}$ of the ${\ensuremath{\eta}}_{c}$ meson have been measured in two-photon interactions at the SLAC ${e}^{+}{e}^{\ensuremath{-}}$ asymmetric $B$ Factory with the BABAR detector. With a sample of approximately 2500 reconstructed ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ decays in $88\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data, the results are ${m}_{{\ensuremath{\eta}}_{c}}=2982.5\ifmmode\pm\else\textpm\fi{}1.1(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.9(\mathrm{syst})\text{ }\mathrm{MeV}/{c}^{2}$ and ${\ensuremath{\Gamma}}_{\mathrm{tot}}^{{\ensuremath{\eta}}_{c}}=34.3\ifmmode\pm\else\textpm\fi{}2.3(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.9(\mathrm{syst})\text{ }\mathrm{MeV}/{c}^{2}$. Using the same decay mode, a second resonance with $112\ifmmode\pm\else\textpm\fi{}24$ events is observed with a mass of $3630.8\ifmmode\pm\else\textpm\fi{}3.4(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.0(\mathrm{syst})\text{ }\mathrm{MeV}/{c}^{2}$ and width of $17.0\ifmmode\pm\else\textpm\fi{}8.3(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}2.5(\mathrm{syst})\text{ }\mathrm{MeV}/{c}^{2}$. This observation is consistent with expectations for the ${\ensuremath{\eta}}_{c}(2S)$ state.

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