Calculation of the α-particle ground state within the hyperspherical harmonic basis

The problem of calculating the four-nucleon bound state properties for the case of realistic two- and three-body nuclear potentials is studied using the hyperspherical harmonic (HH) approach. A careful analysis of the convergence of different classes of HH functions has been performed. A restricted basis is chosen to allow for accurate estimates of the binding energy and other properties of the ⁴He ground state. Results for various modern two-nucleon and two- plus three-nucleon interactions are presented. The origin of the isospin T=1 and T=2 admixtures in the ⁴He ground state is discussed in detail. The ⁴He asymptotic normalization constants for separation in 2+2 and 1+3 clusters are also computed.