Resolving the Λ Hypernuclear Overbinding Problem in Pionless Effective Field Theory.

Area of Science:

• Nuclear Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• The Lambda hypernuclear overbinding problem refers to a 1-3 MeV discrepancy in calculated Lambda separation energies for light hypernuclei, specifically in Helium-5.
• Existing few-body calculations often fail to reproduce experimental ground-state Lambda separation energies using various hyperon-nucleon interaction models.

Purpose of the Study:

• To extend pionless effective field theory (πEFT) nuclear few-body calculations to Lambda hypernuclei.
• To resolve the overbinding problem in light hypernuclei by accurately calculating Lambda separation energies.

Main Methods:

• Extension of recent pionless effective field theory (πEFT) nuclear few-body calculations to Lambda hypernuclei.
• Association of Lambda-N (ΛN) low-energy constants with ΛN scattering lengths at leading order.
• Fitting of Lambda-N-N (ΛNN) low-energy constants to experimental Lambda separation energies (B_Λ^exp) for A≤4.
• Utilization of the few-body stochastic variational method for calculations.

Main Results:

• The developed πEFT interaction accurately reproduces the experimental Lambda separation energy for Helium-5 (B_Λ^exp(Λ^5He) = 3.12±0.02 MeV).
• The calculated value falls within a fraction of a MeV of the experimental value across a wide range of πEFT cutoff parameters.
• The model successfully addresses the overbinding problem in light hypernuclei.

Conclusions:

• The developed pionless effective field theory approach provides a robust framework for understanding Lambda hypernuclear systems.
• The findings suggest potential implications for the study of heavier hypernuclei and neutron star matter.
• This work offers a significant step towards a more accurate description of hyperon-nucleon interactions in nuclear matter.