Search for hidden charm states decaying into<i>J</i>/ψ or ψ’ plus pions

Abstract

A search has been made in 300 GeV/c ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$- and proton-Li interactions for production of states that decay into J/\ensuremath{\psi} or \ensuremath{\psi}' plus one or two pions. A 2.5\ensuremath{\sigma} enhancement in the J/\ensuremath{\psi} ${\mathrm{\ensuremath{\pi}}}^{0}$ spectrum, possibly the recently reported $^{1}$${\mathit{P}}_{1}$ state of charmonium, is observed at a mass of 3.527 GeV/${\mathit{c}}^{2}$. In the J/\ensuremath{\psi} plus two pion mass spectrum, we report, together with the expected \ensuremath{\psi}'\ensuremath{\rightarrow}J/\ensuremath{\psi} ${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$, the tentative observation of a structure at a mass of 3.836 GeV/${\mathit{c}}^{2}$. No enhancements are seen in the J/\ensuremath{\psi} ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$, J/\ensuremath{\psi} ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$${\mathrm{\ensuremath{\pi}}}^{0}$, J/\ensuremath{\psi} ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$, or \ensuremath{\psi}' ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$ mass spectra.