How the Contact Can Produce Snowballs from Hell

Abstract

A loosely bound hadronic molecule produced by a relativistic heavy-ion collision has been described as a "snowball in hell" since it emerges from a hadron gas whose temperature is orders of magnitude larger than the binding energy of the molecule. This remarkable phenomenon can be explained in terms of a novel thermodynamic variable called the "contact" that is conjugate to the binding momentum of the molecule. The production rate of the molecule can be expressed in terms of the contact density at the kinetic freezeout of the hadron gas. It approaches a nonzero limit as the binding energy goes to 0.