Evidence for X(3872) in Pb-Pb Collisions and Studies of its Prompt Production at √sNN=5.02 TeV

The first evidence for X(3872) production in relativistic heavy ion collisions is reported. The X(3872) production is studied in lead-lead (Pb-Pb) collisions at a center-of-mass energy of root s(NN) = 5.02 TeV per nucleon pair, using the decay chain X(3872) -> J/psi pi(+)pi(-) -> mu(+) mu(-) pi(+)pi(-). 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 vertical bar y vertical bar < 1.6 and 15 < p(T) < 50 GeV/c. The significance of the inclusive X(3872) signal is 4.2 standard deviations. The prompt X(3872) to psi 2S yield ratio is found to be rho(Pb-Pb) = 1.08 +/- 0.49(stat) +/- 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.

Automated summary

The first evidence for X(3872) production in relativistic heavy ion collisions is reported. The characteristics of X(3872) in lead-lead collisions are revealed through an analysis of the production process and decay chain. This result provides unique experimental evidence for the production mechanism and nature of X(3872).