He 4 4He + n + n continuum within an ab initio framework

Area of Science:

• Nuclear Physics
• Quantum Mechanics
• Computational Physics

Background:

• The Helium-6 nucleus exhibits complex low-lying continuum spectrum properties.
• Understanding its structure is crucial for nuclear astrophysics and fundamental physics.

Purpose of the Study:

• To investigate the low-lying continuum spectrum of the Helium-6 nucleus.
• To explore the three-cluster dynamics ((4)He + n + n) of its lowest decay channel.
• To identify and characterize nuclear resonances within Helium-6.

Main Methods:

• Utilized an ab initio framework combining the no-core shell model and resonating-group method.
• Solved the three-cluster Schrödinger equation using the hyperspherical-harmonics method on a Lagrange mesh.
• Employed a soft similarity-renormalization-group evolved chiral nucleon-nucleon potential for microscopic calculations.

Main Results:

• Confirmed the known J(π) = 2(+) resonance in Helium-6.
• Found evidence for a new low-lying second 2(+) resonance at 2.6 MeV above the ground state.
• Identified resonances in 2(-), 1(+), and 0(-) channels, with no low-lying resonances in 0(+) and 1(-) channels.

Conclusions:

• The ab initio framework successfully describes the low-lying spectrum of Helium-6.
• The study supports the existence of a newly observed second 2(+) resonance.
• Provides a comprehensive understanding of Helium-6's resonance structure and decay channels.