Fully-heavy tetraquarks in a strongly interacting medium

We study the properties of fully-heavy tetraquarks at finite temperature and their production in high-energy nuclear collisions. We obtain the masses and wave functions of the exotic hadron states cc (c) over bar(c) over bar. and bb (b) over bar(b) over bar by solving the four-body Schrodinger equation in vacuum and strongly interacting matter. In vacuum, the tetraquarks are above the corresponding meson-meson mass threshold, and the newly observed exotic state X(6900) might be a cc (c) over bar(c) over bar state with quantum number J(PC) = 0(++) or 1(+-). In hot medium, the temperature dependence of the tetraquark masses and the dissociation temperatures are calculated. Taking the wave function at finite temperature, we construct the Wigner function for the tetraquark states and calculate, with coalescence mechanism, the production yield and transverse momentum distribution of cc (c) over bar(c) over bar in heavy-ion collisions at LHC energy. In comparison with nucleon-nucleon collisions, the yield per binary collision is significantly enhanced.