Near-threshold $$ \mathrm{D}\overline{\mathrm{D}} $$ spectroscopy and observation of a new charmonium state

AbstractUsing proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector between 2011 and 2018, a new narrow charmonium state, the X(3842) resonance, is observed in the decay modes$$ \mathrm{X}(3842)\to {D}^0{\overline{D}}^0 $$X3842→D0D¯0and X(3842) →D+D−. The mass and the natural width of this state are measured to be$$ \begin{array}{l}{m}_{X(3842)}=3842.71\pm 0.16\pm 0.12\ MeV/{c}^2,\hfill \\ {}{\varGamma}_{X(3842)}=2.79\pm 0.51\pm 0.35\ MeV,\hfill \end{array} $$mX3842=3842.71±0.16±0.12MeV/c2,ΓX3842=2.79±0.51±0.35MeV,where the first uncertainty is statistical and the second is systematic. The observed mass and narrow natural width suggest the interpretation of the new state as the unobserved (spin-3ψ313D3) charmonium state.In addition, prompt hadroproduction of theψ(3770) andχ2(3930) states is observed for the first time, and the parameters of these states are measured to be$$ \begin{array}{l}{m}_{\psi (3770)}=3778.1\pm 0.7\pm 0.6\ MeV/{c}^2,\hfill \\ {}{m}_{\chi_2(3930)}=3921.9\pm 0.6\pm 0.2\ MeV/{c}^2,\hfill \\ {}{\varGamma}_{\chi_2(3930)}=36.6 \pm 1.9 \pm 0.9\ MeV,\hfill \end{array} $$mψ3770=3778.1±0.7±0.6MeV/c2,mχ23930=3921.9±0.6±0.2MeV/c2,Γχ23930=36.6±1.9±0.9MeV,where the first uncertainty is statistical and the second is systematic.