X(3872) in a hot pion bath

Abstract

Right since its discovery in 2003 by the Belle collaboration, establishing the nature of the X(3872) meson has been one of the main priorities in the field of quarkonium physics. Not qualifying as a conventional cc¯ state, the multiquark structure of this exotic meson has received very different interpretations, ranging from a compact tetraquark configuration to an extended DD¯⁎+c.c. molecule. In this work we explore the effect that a hot pion bath may have in the properties of the X(3872), assuming this state to be a DD¯⁎+c.c. molecule. We derive the finite temperature effects on the X(3872) from a coupled channels unitarized amplitude, obtained including the properties of the charmed mesons under such conditions. We find that the X(3872) develops a subtantial width, of the order of a few tens of MeV, in hot pionic environments at temperatures 100-150 MeV, and its nominal mass moves above the DD⁎ threshold. The fact that the X(3872) in a hot pion gas may no longer be a narrow resonance needs to be considered in the estimation of production yields in relativistic heavy-ion collisions. Keywords: Ultrarelativistic heavy ion collisions, Charm mesons, Exotic hadrons, X(3872), Hadron molecules, Hadron properties in medium