Pion absorption from the lowest atomic orbital in 2H, 3H, and 3He

The ????? +2H ??? n+n, ????? + 3H ??? n+n+n, ?????+ 3He ??? n+d, and ????? +3He ??? p+n+n capture reactions from the lowest 1S atomic orbitals are studied under full inclusion of final state interactions. Our results are obtained with the single-nucleon and two-nucleon transition operators derived at leading order in chiral effective field theory. The initial and final three-nucleon states are calculated with the chiral nucleon-nucleon semilocal momentum space potential up to N4LO+, augmented by the consistently regularized chiral N2LO three-nucleon potential. We found that absorption rates depend strongly on the nuclear pion absorption operator used, and its two-body parts change the rates by a few orders of magnitude. The final state interactions between nucleons generated by the two-nucleon forces are also important, while the three-nucleon interaction plays a visible role only in the ????? + 3He??? n + d reaction. Our absorption rate for the ????? + 2H??? n + n process is in good agreement with the experimental data from the hadronic ground-state broadening in pionic deuterium. The capture rates on 3He are also generally consistent with the spectroscopic data within error bars, though our central values are found to be systematically below the data. We show that for the three-body breakup processes the dominant contributions to the absorption rates arise from the quasi-free scattering and final-state interaction kinematical configurations.

Automated summary

In this study, absorption reactions are investigated using single-nucleon and two-nucleon transition operators derived from chiral effective field theory. The results show that the absorption rates strongly depend on the nuclear pion absorption operator used and the two-body parts of the operator significantly affect the rates. The final state interactions between nucleons generated by two-nucleon forces are important, while the three-nucleon interaction plays a visible role only in certain reactions.