Isolating the Λ(1405) in lattice QCD.

Area of Science:

• Particle Physics
• Quantum Chromodynamics (QCD)

Background:

• The Lambda (Λ) baryon's odd-parity ground state has a surprisingly low mass (1405 MeV).
• This mass is lower than the odd-parity ground-state nucleon, despite the Λ baryon containing a strange quark.

Purpose of the Study:

• To isolate and study the elusive odd-parity ground state of the Λ baryon.
• To determine if the calculated mass ordering matches experimental observations relative to scattering thresholds.

Main Methods:

• Utilized (2+1)-flavor full-QCD ensembles from the PACS-CS collaboration.
• Employed a variational analysis technique with source and sink smearing.
• Used a partially quenched strange quark to achieve the correct kaon mass.

Main Results:

• Successfully isolated the odd-parity Λ baryon state.
• Reproduced the correct level ordering with respect to nearby scattering thresholds for the first time.
• Observed a low-lying, odd-parity mass trend consistent with experimental values.

Conclusions:

• The study confirms the surprisingly low mass of the odd-parity Λ baryon.
• The findings align with experimental data, validating the computational methods used.
• This research provides crucial insights into the properties of strange baryons within QCD.