Density-Induced Hadron-Quark Crossover via the Formation of Cooper Triples

We discuss the hadron-quark crossover accompanied by the formation of Cooper triples (three-body counterpart of Cooper pairs) by analogy with the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer crossover in two-component fermionic systems. Such a crossover is different from a phase transition, which often involves symmetry breaking. We calculate the in-medium three-body energy from the three-body T-matrix with a phenomenological three-body force characterizing a bound hadronic state in vacuum. With increasing density, the hadronic bound-state pole smoothly undergoes a crossover toward the Cooper triple phase where the in-medium three-body clusters coexist with the quark Fermi sea. The relation to the quarkyonic matter model can also be found in a natural manner.

Automated summary

We discuss the hadron-quark crossover accompanied by the formation of Cooper triples and draw an analogy with the Bardeen-Cooper-Schrieffer crossover in fermionic systems. This crossover, unlike a phase transition, does not involve symmetry breaking. We calculate the in-medium three-body energy using a phenomenological three-body force and observe a smooth crossover from the hadronic bound-state pole to the Cooper triple phase as density increases. The coexistence of three-body clusters and quark Fermi sea in the crossover is also related to the quarkyonic matter model.