Probing the nature of the ${\chi }_{c1}(3872)$ state using radiative decays

Abstract

The radiative decays ${\chi }_{c1}(3872)\to \psi (2S)\gamma$ and ${\chi }_{c1}(3872)\to J/\psi \gamma$ are used to probe the~nature of the~${\chi }_{c1}(3872)$ state using proton-proton collision data collected with the LHCb detector, corresponding to an~integrated luminosity of~9fb${}^{-1}$. Using the~$B^{+}\to {\chi }_{c1}(3872)K^{+}$decay, the ${\chi }_{c1}(3872)\to \psi (2S)\gamma$ process is observed for the first time and the ratio of its partial width to that of the ${\chi }_{c1}(3872)\to J/\psi \gamma$ decay is measured to be $$\frac{{\Gamma }_{{\chi }_{c1}(3872)\to \psi (2S)\gamma }}{{\Gamma }_{{\chi }_{c1}(3872)\to J/\psi \gamma }}=1.67\pm 0.21\pm 0.12\pm 0.04,$$ where the first uncertainty is statistical, the second systematic and the third is due to the uncertainties on the branching fractions of the $\psi (2S)$ and $J/\psi$ mesons. The measured ratio makes the interpretation of the ${\chi }_{c1}(3872)$ state as a~pure $D^0{\bar{D}}^{\ast 0}+{\bar{D}}^0{D}^{\ast 0}$ molecule questionable and strongly indicates a sizeable compact charmonium or tetraquark component within the ${\chi }_{c1}(3872)$ state.

arXiv comment31 pages, 2 figures. All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2024-015.html (LHCb public pages)

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Cited by in corpus (8)

• The nature of ${\chi }_{c1}\left(3872\right)$ and $T_{cc}^{+}\left(3875\right)$
• Charmonium: Conventional and $XYZ$ States in a Relativistic Screened Potential Model
• A short review on the compositeness of the $X(3872)$
• The charmonium-like exotic hadron productions in $e^{+}{e}^{-}$ collisions at the BESIII energy with the PACIAE model
• Two nearby states in the $X(3872)$ region: Resolving the radiative-decay ratio tension with ${\eta }_{c2}$
• What can we learn from the radiative decays of the $D_{s1}(2460)$ meson?
• Electromagnetic probes revealing the inner structure of the ${\Lambda }_c(2940)$
• Observation of the decay ${\chi }_{c1}(3872)\to J/\psi {\mu }^{+}{\mu }^{-}$