Abstract
The first evidence for X(3872) in heavy ion collisions is reported. Prompt X(3872) production is studied with the CMS detector in PbPb collisions at a center-of-mass energy of √sNN =5.02TeV per nucleon pair, using the decay chain X(3872)→ J/ψπ+π− → μ+μ−π+π−. The measurement is performed in a kinematic range in which the X(3872) candidates have a transverse momentum 15 < pT < 50GeV/c and rapidity |y| < 1.6. The statistical significance of the X(3872) signal is in excess of 3 standard deviations. The production and survival of the prompt X(3872) in the quark-gluon plasma is expected to depend upon its internal structure. The ratio of the X(3872) and ψ(2S) yields is found to be R = 1.10 ± 0.51 (stat.) ± 0.53 (syst.) and is compared to the ratio measured in pp collisions at √s=7and8TeV.
