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

TL;DR

This paper explores a smooth hadron-quark crossover driven by the formation of three-body Cooper triples, providing a new perspective on the transition without symmetry breaking, relevant to quarkyonic matter.

Contribution

It introduces the concept of Cooper triples in the hadron-quark crossover and models their formation using in-medium three-body energy calculations.

Findings

Smooth crossover from hadronic bound states to Cooper triples

Coexistence of three-body clusters with quark Fermi sea at high density

Connection to quarkyonic matter model

Abstract

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.