Probing the hadron mass spectrum in dense two-color QCD with the linear sigma model

TL;DR

This paper models how hadron masses change with density in dense two-color QCD using a linear sigma model, revealing complex mixing effects and chiral partner structures that can guide future lattice simulations.

Contribution

It introduces a comprehensive linear sigma model incorporating excited states and symmetry effects to analyze hadron mass modifications at finite density in two-color QCD.

Findings

Rich hadron mass spectrum due to mixing effects

Influence of $U(1)_A$ anomaly on mass behavior

Manifestation of chiral partner structures with increasing density

Abstract

We investigate modifications of hadron masses at finite quark chemical potential in two-flavor and two-color QCD, of which the data are available from lattice simulations, within a linear sigma model based on approximate Pauli-Gursey $SU(4)$ symmetry. The model describes not only ground-state scalar diquarks and pseudo-scalar mesons but also the excited pseudo-scalar diquarks and scalar mesons; each ground-state diquark (meson) has the corresponding excited diquark (hadron) with opposite parity as a chiral partner. Effects of chiral symmetry breaking and diquark condensates are incorporated by a mean-field treatment. We show that various mixings among the hadrons, which are triggered by the breakdown of baryon number conservation in the superfluid phase, lead to a rich hadron mass spectrum. We discuss the influence of $U(1)_A$ anomaly on the density dependence of the mass spectrum and also manifestations of the chiral partner structures as density increases in the superfluid phase. The predicted hadron masses are expected to provide future lattice simulations with useful information on such symmetry properties in dense two-color QCD.