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

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## Abstract

Using 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 $X(3842)\rightarrow D^0\bar{D}^0$ and $X(3842)\rightarrow D^+D^-$. The mass and the natural width of this state are measured to be \begin{eqnarray*} m_{X(3842)} & = & 3842.71 \pm 0.16 \pm 0.12 MeV/c^2 , \Gamma_{X(3842)} & = & 2.79 \pm 0.51 \pm 0.35 MeV , \end{eqnarray*} 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\nobreakdash-3 $\psi_3\mathrm{\left(1^3D_3\right)}$ charmonium state. In addition, prompt hadroproduction of the $\psi(3770)$ and $\chi_{c2}(3930)$ states is observed for the first time, and the parameters of these states are measured to be \begin{eqnarray*} m_{\psi(3770)} & = & 3778.1 \pm 0.7 \pm 0.6 MeV/c^2 , m_{\chi_{c2}(3930)} & = & 3921.9 \pm 0.6 \pm 0.2 MeV/c^2 , \Gamma_{\chi_{c2}(3930)} & = &36.6 \pm 1.9 \pm 0.9 MeV , \end{eqnarray*} where the first uncertainty is statistical and the second is systematic.

## Supplementary Material [file]

 Supplementary material full pdf supple[..].pdf [195 KiB] This ZIP file contains supplemetary material for the publication LHCb-PAPER-2019-005. The files are: Supplementary.pdf : An overview of the extra figures *.pdf : The figures in pdf format Fig1a_supp.pdf [7 KiB] HiDef png [85 KiB] Thumbnail [69 KiB] *C file Fig1b_supp.pdf [7 KiB] HiDef png [77 KiB] Thumbnail [62 KiB] *C file Fig2_supp.pdf [9 KiB] HiDef png [103 KiB] Thumbnail [93 KiB] *C file

Created on 18 October 2019.