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

Abstract

Using proton-proton collision data, corresponding to an integrated luminosity of 9$f{b}^{-1}$, collected with the~LHCb detector between 2011 and 2018, a new narrow charmonium state, the $X(3842)$ resonance, is observed in the decay modes $X(3842)\to D^0{\bar{D}}^0$ and $X(3842)\to D^{+}{D}^{-}$. 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\,, Γ_{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 ${\psi }_3\left(1^3{\mathrm{D}}_3\right)$ 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_{ψ(3770)} & = & 3778.1 \pm 0.7 \pm 0.6 MeV/c^2\,, m_{χ_{c2}(3930)} & = & 3921.9 \pm 0.6 \pm 0.2 MeV/c^2\,, Γ_{χ_{c2}(3930)} & = &36.6 \pm 1.9 \pm 0.9 MeV\,, \end{eqnarray*} where the first uncertainty is statistical and the~second is systematic.

arXiv comment21 pages, 5 figures. All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2019-005.html

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• LHCb Detector Performance
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• Properties of heavy quarkonia and B_c mesons in the relativistic quark model
• Decay Chain Fitting with a Kalman Filter
• Performance of the LHCb Outer Tracker
• Charmonium Options for the X(3872)
• Heavy Mesons In A Relativistic Model
• Mass distributions marginalized over per-event errors
• Improved performance of the LHCb Outer Tracker in LHC Run 2
• New states above charm threshold
• Line Shapes of the X(3872)
• Potential model calculations and predictions for heavy quarkonium
• B-Meson Gateways to Missing Charmonium Levels
• Could the $X(3915)$ and the $X(3930)$ Be the Same Tensor State?
• Analysis of J/psi pi+ pi- and D0 D0-bar pi0 Decays of the X(3872)
• Measurement of ψ(3770) parameters
• Analysis of BaBar, Belle, BES-II, CLEO and KEDR data on $\psi (3770)$ line shape and determination of the resonance parameters

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