The negative-parity spin-1/2 $\Lambda$ baryon spectrum from lattice QCD and effective theory

TL;DR

This study compares lattice QCD and effective theory approaches to the negative-parity spin-1/2 Lambda baryon spectrum, finding good agreement for certain states but noting the absence of meson-baryon scattering signals in current lattice results.

Contribution

It demonstrates the consistency between lattice QCD and effective theory in identifying Lambda baryon states and explores their quark mass dependence, highlighting current limitations in lattice operator choices.

Findings

Lattice QCD states match one of the two Lambda(1405) poles and the Lambda(1670) resonance.

Quark mass dependence of lattice levels agrees with effective theory.

Meson-baryon scattering states are not yet observed in lattice QCD.

Abstract

The spectrum of the negative-parity spin-1/2 $\Lambda$ baryons is studied using lattice QCD and hadronic effective theory in a unitarized coupled-channel framework. A direct comparison between the two approaches is possible by considering the hadronic effective theory in a finite volume and with hadron masses and mesonic decay constants that correspond to the situation studied on the lattice. Comparing the energy level spectrum and $SU(3)$ flavor decompositions of the individual states, it is found that the lowest two states extracted from lattice QCD can be identified with one of the two $\Lambda(1405)$-poles and the $\Lambda(1670)$ resonance. The quark mass dependences of these two lattice QCD levels are in good agreement with their effective theory counterparts. However, as current lattice QCD studies still rely on three-quark operators to generate the physical states, clear signals corresponding to the meson-baryon scattering states, that appear in the finite volume effective theory calculation, are not yet seen.