Quantum Monte Carlo Calculations of Neutron-$\alpha$ Scattering

We describe a new method to treat low-energy scattering problems in few-nucleon systems, and we apply it to the five-body case of neutron-alpha scattering. The method allows precise calculations of low-lying resonances and their widths. We find that a good three-nucleon interaction is crucial to obtain an accurate description of neutron-alpha scattering.

Figure 1

Phase shifts for $n\mathrm{\text{−}}\alpha$ scattering. Filled symbols (with statistical errors smaller than the symbols) are GFMC results; dashed curves are fits described in the text; and solid curves are from an $R$-matrix fit to data [16].

Figure 2

Partial-wave cross sections from the $\mathrm{AV}18+\mathrm{IL}2$ Hamiltonian compared to $R$-matrix analysis. Stars show the pole energies in $3/2^{-}$ scattering for the $R$-matrix fit and for $\mathrm{AV}18+\mathrm{IL}2$, with the bars indicating the imaginary part.