X(3872) Transport at the LHC

Abstract

The production yields of the X(3872) particle in heavy-ion collisions have been suggested to be sensitive to its internal structure. While the thermal equilibrium limit of the X(3872)abundance only depends on its mass, its inelastic reaction rates in a hot medium are expected to be different depending on whether it is a loosely bound hadronic molecule or a compact tetraquark dominated by colored diquark-antidiquark configurations. Here we implement these scenarios into a kinetic rate equation as previously used in applications to charmonium and bottomonium observables. While the equilibrium limit, controlled by the charm-quark content in the fireball, is universal for both scenarios (and decreases with temperature), the molecular scenario is characterized by a much larger width in the hadronic medium than for the tetraquark. Consequently, the average production time of the molecular X(3872)is significantly later than for the tetraquark, leading to to a factor of ∼2 smaller production of the former compared to the latter. This outcome is qualitatively different from most coalescence model calculations to date. In addition, we calculate pertinent transverse-momentum spectra, which turn out to be harder for the molecular scenario due to the larger blue-shift caused by the collective flow in the fireball at later times.