New Resonances in \(\mathbf{J/}{\psi}\mathbf{J/}{\psi}\) Mass Spectrum at CMS

Abstract

A search is reported for near-threshold resonances decaying to \(\textrm{J}/\psi\textrm{J}/\psi\), using the 13 TeV proton–proton collision data collected by the CMS experiment. Two structures are observed at masses of about 6550 and 6930 MeV with local significance exceeding 5 standard deviations. The second one is consistent with the X(6900) previously reported by the LHCb experiment. Evidence for a third structure is found at about 7300 MeV with a local significance of 4 standard deviations. Models employing interference between these states were tested and can provide a better description of the spectrum between the resonances.