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Abstract. The π− + 2H → n + n, π− + 3H → n + n + n, π− + 3He → n + d and π− + 3He → p + n + n capture reactions from the lowest atomic orbitals are investigated under full inclusion of final state interactions and employing the single-nucleon and two-nucleon transition operators derived at leading order in chiral effective field theory.

We investigate the π– + 2H → γ + n + n, π– + 3He → γ + 3H, π– + 3He → γ + n + d, π– + 3He → γ + n + n + p and π– + 3H → γ + n + n + n capture reactions using realistic two-nucleon and three-nucleon potentials and the single nucleon Kroll-Ruderman-type transition operator. We obtain predictions for the total capture rates for all these processes, calculating rigorously the initial and final nuclear states.

The JISP16 nucleon-nucleon potential is applied to investigate the nucleon induced deuteron breakup reaction at energies E=13 and 65 MeV. Our study reveals that this force delivers, in general, a qualitatively similar description of the exclusive cross section for the studied reaction to the one based on the standard realistic nucleon-nucleon AV18 interaction. However, in some regions of the phase space the differential cross sections based on the JISP16 and on the AV18 forces differ by more than 100% and 50% at E=13 MeV and E=65 MeV, respectively. Such specific parts of the phase space can be used to fine-tune the JISP16 potential parameters.

The traditional method of carrying out few-nucleon calculations is based on the angular momentum decomposition of operators relevant to the calculation. Expressing operators using a finite-sized partial wave basis enables the calculations to be carried out using a small amount of numerical work. Unfortunately, certain calculations that involve higher energies or long range potentials, require including a large number of partial waves in order to get converged results. This is problematic because such an approach requires a numerical implementation of heavily oscillating functions. Modern computers made it possible to carry out few-nucleon calculations without using angular momentum decomposition and instead to work directly with the three dimensional degrees of freedom of the nucleons. In this paper we briefly describe the, so called 3D approach and present preliminary results related to the 3He bound state obtained within this formalism.

Results on three-nucleon (3N) elastic scattering and breakup below the pion production threshold are discussed. The large discrepancies found between a theory based on numerical solutions of 3N Faddeev equations with standard nucleon-nucleon (NN) potentials only and data point to the need for three-nucleon forces (3NF’s). This notion is supported by the fact that another possible reason for the discrepancies in elastic nucleon-deuteron (Nd) scattering, relativistic effects, turned out to be small. Results for a new generation of chiral NN forces (up to N4LO) together with theoretical truncation errors are shown. They support conclusions obtained with standard NN potentials

We present a three-dimensional (3D) description of muon induced deuteron disintegration. This reaction is treated as the decay of the muonic atom with the muon initially on the lowest K shell. Our aim is to calculate the total and differential decay rates. We work in momentum space and use 3D momentum eigenstates directly. This approach allowed us to calculate the appropriate nuclear matrix elements, necessary building blocks for the differential decay rate, in a single step. For contrast - in classical calculations many partial-waves have to be taken into account. We achieved a very good agreement between the 3D and partial-wave methods for calculations that involve single-nucleon currents. Our result for the total decay rate is also in agreement with experimental values, though these are not very precise. This success motivates us to also include two-nucleon current contributions that include the meson exchange currents. Additionally, our formalism can also be applied to other, so far poorly described, processes like: μ +3 He→ ν + n + d or μ +3 He → ν + n + n + p.

We study the elastic nucleon-deuteron scattering process at incomingnucleon laboratory energies up to E = 200 MeV working within the formalism of Faddeev equations. We focused here on the computation and systematic analysis of the correlation coefficients among various observables in nucleon-nucleon and nucleon-deuteron elastic scattering. As a result, we obtained pairs of correlated/uncorrelated observables or sets of very weakly correlated observables. The knowledge, if some observables are or are not correlated, would impact future methods of fixing free parameters of the two- and many-body potentials, and could possibly help determine observables which should be measured to increase the precision of potential parameters' determination. [ABSTRACT FROM AUTHOR]

The JISP16 nucleon-nucleon potential has been applied to explore the nucleon-induced deuteron breakup process at the incoming nucleon laboratory energy E = 65 MeV. We have found that the JISP16 model generally gives predictions for the differential cross section and the nucleon analysing power, which are similar to the ones obtained with the standard realistic nucleon-nucleon AV18 potential. However, there are some regions of the phase space, for which the cross section and the analysing power differ by approximately 50%. These kinematical configurations could be used to refit the JISP16 potential parameters. [ABSTRACT FROM AUTHOR]