The ${ ^3{ \rm He}}(\alpha,\gamma){ ^7{ \rm Be}}$ and ${ ^3{ \rm H}}(\alpha,\gamma){ ^7{ \rm Li}}$ astrophysical $S$ factors are calculated within the no-core shell model with continuum using a renormalized chiral nucleon-nucleon interaction. The ${ ^3{ \rm He}}(\alpha,\gamma){ ^7{ \rm Be}}$ astrophysical $S$ factors agree reasonably well with the experimental data while the ${ ^3{ \rm H}}(\alpha,\gamma){ ^7{ \rm Li}}$ ones are overestimated. The seven-nucleon bound and resonance states and the $\alpha+{ ^3{ \rm He}}/{ ^3{ \rm H}}$ elastic scattering are also studied and compared with experiment. The low-lying resonance properties are rather well reproduced by our approach. At low energies, the $s$-wave phase shift, which is non-resonant, is overestimated.
Categories: nucl-th astro-ph.SR nucl-ex