Optimized chiral nucleon-nucleon interaction at next-to-next-to-leading order

Area of Science:

• Nuclear Physics
• Quantum Chromodynamics
• Effective Field Theory

Background:

• Chiral effective field theory provides a systematic framework for describing nuclear forces.
• Previous parametrizations of chiral interactions required significant contributions from three-nucleon forces.

Purpose of the Study:

• To optimize the nucleon-nucleon interaction within chiral effective field theory at next-to-next-to-leading order (NNLO).
• To develop a new chiral force, NNLO(opt), that improves the description of nuclear systems.
• To investigate the necessity of three-nucleon forces in nuclear structure calculations.

Main Methods:

• Optimization of the nucleon-nucleon interaction from chiral effective field theory.
• Fitting the interaction to experimental data for laboratory energies below approximately 125 MeV.
• Application of the optimized force to A=3, 4 nucleon systems and neutron matter.

Main Results:

• The new chiral force, NNLO(opt), achieves a statistically excellent fit (χ(2)≈1 per degree of freedom).
• Contributions of three-nucleon forces are found to be smaller with NNLO(opt) compared to previous chiral forces.
• NNLO(opt) successfully describes properties of key nuclei and neutron matter.

Conclusions:

• The optimized nucleon-nucleon interaction provides a robust description of nuclear properties.
• Many aspects of nuclear structure can be understood using only the optimized two-nucleon interaction.
• This work reduces the reliance on explicit three-nucleon forces in nuclear theory.