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arXiv · 2102.13048

Evidence for X(3872) in PbPb collisions and studies of its prompt production at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

CMS Collaboration
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Abstract

The first evidence for X(3872) production in relativistic heavy ion collisions is reported. The X(3872) production is studied in lead-lead (PbPb) collisions at a center-of-mass energy of $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV per nucleon pair, using the decay chain X(3872) $\to$ J$/ψ\, π^+π^- \to$ $μ^+μ^-π^+π^-$. The data were recorded with the CMS detector in 2018 and correspond to an integrated luminosity of 1.7 nb$^{-1}$. The measurement is performed in the rapidity and transverse momentum ranges $|y|$ $\lt$ 1.6 and 15 $\lt$ $p_\mathrm{T}$ $\lt$ 50 GeV$/c$. The significance of the inclusive X(3872) signal is 4.2 standard deviations. The prompt X(3872) to $ψ$(2S) yield ratio is found to be $ρ^\mathrm{PbPb} = $ 1.08 $\pm$ 0.49 (stat) $\pm$ 0.52 (syst), to be compared with typical values of 0.1 for pp collisions. This result provides a unique experimental input to theoretical models of the X(3872) production mechanism, and of the nature of this exotic state.

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CMS Collaboration. 2022-01-20. Evidence for X(3872) in PbPb collisions and studies of its prompt production at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV. https://doi.org/10.1103/physrevlett.128.032001

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