Flavor structure of $\Lambda$ baryons from lattice QCD: From strange to charm quarks

Abstract

We study $\Lambda$ baryons of spin-parity ${\frac{1}{2}}^{\pm }$ with either a strange or charm valence quark in full 2+1 flavor lattice QCD. Multiple $SU(3)$ singlet and octet operators are employed to generate the desired single baryon states on the lattice. Via the variational method, the couplings of these states to the different operators provide information about the flavor structure of the $\Lambda$ baryons. We make use of the gauge configurations of the PACS-CS Collaboration and chirally extrapolate the results for the masses and $SU(3)$ flavor components to the physical point. We furthermore gradually change the hopping parameter of the heaviest quark from strange to charm to study how the properties of the $\Lambda$ baryons evolve as a function of the heavy quark mass. It is found that the baryon energy levels increase almost linearly with the quark mass. Meanwhile, the flavor structure of most of the states remains stable, with the exception of the lowest ${\frac{1}{2}}^{-}$ state, which changes from a flavor singlet $\Lambda$ to a ${\Lambda }_c$ state with singlet and octet components of comparable size. Finally, we discuss whether our findings can be interpreted with the help of a simple quark model and find that the negative-parity ${\Lambda }_c$ states can be naturally explained as diquark excitations of the light $u$ and $d$ quarks. On the other hand, the quark-model picture does not appear to be adequate for the negative-parity $\Lambda$ states, suggesting the importance of other degrees of freedom to describe them.

14 pages, 8 figures, 5 tables; v2 (published version in PRD): title slightly changed, discussion about systematic uncertainties extended, typos fixed, references added

References in corpus (5)

• Effective Kbar N interaction based on chiral SU(3) dynamics
• Lattice QCD Evidence that the Lambda(1405) Resonance is an Antikaon-Nucleon Molecule
• Excited hadrons on the lattice: Baryons
• Vector and axial-vector couplings of D and D* mesons in 2+1 flavor Lattice QCD
• Five-quark picture of Lambda(1405) in anisotropic lattice QCD

Cited by in corpus (12)

• Review of the $\mathbf{\Lambda }$(1405): A curious case of a strange-ness resonance
• QCD and the Strange Baryon Spectrum
• Charmed baryon spectrum from lattice QCD near the physical point
• Novel approaches in Hadron Spectroscopy
• Two-pole nature of the $\Lambda (1405)$ from lattice QCD
• Lattice QCD study of $\pi \Sigma -\bar{K}N$ scattering and the $\Lambda (1405)$ resonance
• The negative-parity spin-1/2 $\Lambda$ baryon spectrum from lattice QCD and effective theory
• Charm-baryon semileptonic decays and the strange ${\Lambda }^{\ast }$ resonances: New insights from lattice QCD
• Structure of the $\mathbf{\Lambda }(1670)$ resonance
• Pole trajectories of the $\Lambda (1405)$ helps establish its dynamical nature
• Exotic properties of N^*(1895) and its impact on photoproduction of light hyperons
• The $\Lambda (1405)$ resonance as a genuine three-quark or molecular state