Observation and Properties of theX(3872)Decaying toJ/ψπ+π−inpp¯Collisions ats=1.96 TeV

We report the observation of the $X(3872)$ in the $J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ channel, with $J/\ensuremath{\psi}$ decaying to ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, in $p\overline{p}$ collisions at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{T}\mathrm{e}\mathrm{V}$. Using approximately $230\text{ }\text{ }{\mathrm{p}\mathrm{b}}^{\ensuremath{-}1}$ of data collected with the Run II D0 detector, we observe $522\ifmmode\pm\else\textpm\fi{}100$ $X(3872)$ candidates. The mass difference between the $X(3872)$ state and the $J/\ensuremath{\psi}$ is measured to be $774.9\ifmmode\pm\else\textpm\fi{}3.1(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}3.0(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\text{ }\text{ }\mathrm{M}\mathrm{e}\mathrm{V}/{c}^{2}$. We have investigated the production and decay characteristics of the $X(3872)$ and find them to be similar to those of the $\ensuremath{\psi}(2S)$ state.

Observation and Properties of theX(3872)Decaying toJ/ψπ+π−inpp¯Collisions ats=1.96 TeV | Litlas