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An experiment was proposed to determine the low-energy parameters of the np interaction in the nd breakup reaction at a neutron energy of 5 MeV in the RADEX neutron channel, Institute for Nuclear Research, Russian Academy of Sciences, Moscow, Russia. The energy of the virtual 1S0 state and the np scattering length can be obtained from the experimental dependence of the reaction yield on the relative energy of motion of the breakup neutron and proton in the kinematic region, where the np interaction in the final state is most pronounced. The reaction events were simulated, based on which the optimal conditions for the future experiment were selected. [ABSTRACT FROM AUTHOR]

During the past two decades, chiral effective field theory has evolved into a powerful tool to derive nuclear forces from first principles. Nearly all two-nucleon interactions have been worked out up to sixth order of chiral perturbation theory, while, with few exceptions, three-nucleon forces, which play a subtle, but crucial role in microscopic nuclear structure calculations, have been derived up to fifth order. We review the current status of these forces as well as their applications in nuclear many-body systems. While the ab initio description of light nuclei is generally very successful, we point out and analyze problems encountered with medium-mass nuclei. We also survey the construction of equations of state for symmetric nuclear matter and neutron-rich matter based on chiral forces. A focal point is the symmetry energy and its impact on neutron skins and systems of astrophysical relevance. The physics of neutron-rich systems, from nuclei to compact stars, is essentially determined by the density dependence of the symmetry energy. We review the status of predictions in comparison with latest empirical constraints, with particular attention to those extracted from parity-violating electron scattering. [ABSTRACT FROM AUTHOR]

Abstract The equation of state of neutron and symmetric matter is calculated within the lowest order constrained variational (LOCV) method using the Argonne V18 (AV18) nucleon–nucleon interaction supplemented by the local, coordinate space versions of the chiral three-nucleon force (TNF) at next-to-next-to-leading order (N2LOL). We present the first results of studying the nuclear equation of state in the LOCV framework by employing a chiral TNF. It is shown that although some calculated values of saturation properties lie well in the empirically determined ranges, all of the saturation quantities can not be predicted simultaneously. We also study other possible parametrizations of the N2LOL TNF by fitting the low-energy constants (LECs) to nuclear saturation point. It is found that by employing the proposed sets of LECs, LOCV method is able to successfully produce the equilibrium properties of symmetric nuclear matter. [ABSTRACT FROM AUTHOR]

We review the impact of nuclear forces on matter at neutron-rich extremes. Recent results have shown that neutron-rich nuclei become increasingly sensitive to three-nucleon forces, which are at the forefront of theoretical developments based on effective field theories of quantum chromodynamics. These developments include the formation of shell structure, the spectroscopy of exotic nuclei, and the location of the neutron drip line. Nuclear forces also constrain the properties of neutron-rich matter, including the neutron skin, the symmetry energy, and the structure of neutron stars. First, we review our understanding of three-nucleon forces and show how chiral effective field theory makes unique predictions for many-body forces. Then, we survey results with three-nucleon forces in neutron-rich oxygen and calcium isotopes and neutron-rich matter, which have been explored with a range of many-body methods. Three-nucleon forces therefore provide an exciting link between theoretical, experimental, and observational nuclear physics frontiers. [ABSTRACT FROM AUTHOR]

Abstract: A comprehensive data set is reported for the two-body photodisintegration cross section of 3He using mono-energetic photon beams at eleven energies between 7.0 and 16.0 MeV. A high-pressure gas scintillator served as target and detector. Although our data are in much better agreement with our state-of-the-art theoretical calculations than the majority of the previous data, these calculations underpredict the new data by about 10%. This disagreement suggests an incomplete understanding of the dynamics of the three-nucleon system and its response to electromagnetic probes. [Copyright &y& Elsevier]

Cross section and analyzing power Ay of $^2 {\rm H}(\vec p,p)pn$ reaction at $E_{\vec p} = 247\, {\rm MeV}$ were measured and large disagreements with 3N calculations were found especially at forward angles. Effects of 2π3NF are too small to explain the discrepancy. To microscopically investigate the discrepancy, a 2H(p, pp)n experiment is planned. [ABSTRACT FROM AUTHOR]

We made again an experiment of pd radiative capture at $E_{\vec d} = 197\, {\rm MeV}$, and obtained Axx, Ayy and Azz (= -Axx - Ayy) data using a newly-developed data-analysis method of high detection efficiency. Re-analysis of previous data on Axx and Ayy was also made using a new method. All the new and previous data at 197 MeV agree to each other, and Axx anomaly has been confirmed. [ABSTRACT FROM AUTHOR]

A large set of high precision cross sections, vector Ax, Ay and tensor Axx, Axy, Ayy analyzing powers for the $^1 H(\vec d, pp)n$ breakup reaction were measured at 130 MeV beam energy with the detection system covering a large part of the phase space. Results are compared with rigorous theoretical calculations employing various models of the three-nucleon system dynamics. The cross section data allowed to establish evidence for three-nucleon force contributions and to confirm predictions of sizable effect of the Coulomb force in the breakup reaction. Analyzing power data are generally quite well described by theoretical predictions even with pure NN interactions. However, in some regions discrepancies has been observed for tensor analyzing powers, only rarely cured by inclusion of the three nucleon force. This indicates incompletness of the present-day treatment of the spin part of three nucleon system dynamics. [ABSTRACT FROM AUTHOR]

Abstract: The neutron–deuteron elastic scattering differential cross section has been measured at 95 MeV incident neutron energy. The neutron–proton differential cross section has also been measured for normalization purposes. An inclusion of three-nucleon forces gives a considerable improvement in the theoretical description of the nd data in the angular region of the cross-section minimum. [Copyright &y& Elsevier]

Rich sets of high precision cross sections, vector and tensor analyzing powers for the $^1 H(\vec d,pp)n$ breakup reaction were measured at 130 and 100 MeV beam energy with the use of detection systems covering large parts of the phase space. The cross section data allowed to establish evidences for three-nucleon force contributions and to confirm predictions of sizable effect of the Coulomb force in the breakup reaction. Analyzing power data are generally quite well described by theoretical predictions even with pure nucleon-nucleon interactions. However, in some regions discrepancies has been observed for tensor analyzing powers at 130 MeV. [ABSTRACT FROM AUTHOR]

Three-nucleon force and continuum play important roles in reproducing the properties of atomic nuclei around driplines. Therefore it is valuable to build up a theoretical framework where both effects can be taken into account to solve the nuclear Schrödinger equation. To this end, in this letter, we have expressed the chiral three-nucleon force within the continuum Berggren representation, so that bound, resonant and continuum states can be treated on an equal footing in the complex-momentum space. To reduce the model dimension and computational cost, the three-nucleon force is truncated at the normal-ordered two-body level and limited in the sd -shell model space, with the residual three-body term being neglected. We choose neutron-rich oxygen isotopes as the test ground because they have been well studied experimentally, with the neutron dripline determined. The calculations have been carried out within the Gamow shell model. The quality of our results in reproducing the properties of oxygen isotopes around the neutron dripline shows the relevance of the interplay between three-nucleon force and the coupling to continuum states. We also analyze the role played by the chiral three-nucleon force, by dissecting the contributions of the 2 π exchange, 1 π exchange and contact terms. [ABSTRACT FROM AUTHOR]

Abstract: Results on nucleon-deuteron (Nd) elastic scattering and deuteron breakup below the pion production threshold are discussed emphasizing the need for a three-nucleon force (3NF). Precise solutions of the three-nucleon (3N) Faddeev equations with realistic (semi)phenomenological nucleon-nucleon (NN) potentials alone are insufficient to describe the data. Results involving in addition standard 3NF models like the 2π-exchange TM99 force are presented, which, however, are usually insufficient as well. Relativistic effects turn out to be small. These two observations point to the need of short range 3NF components. Chiral perturbation theory (χPT) provides 3NF''s which go beyond the 2π-exchange including a one –π-exchange-contact force and a pure 3N-contact force at the lowest order of their occurrence. Their application at the higher energies yields results which are qualitatively and quantitatively different from the results of the standard NN and 3NF models. Though somewhat stretched beyond their proper domain of applicability of that type of forces this supports the conclusion of an increased importance of short range 3NF''s at those higher energies. The consistent χPT forces carried to higher orders can be expected to establish the final form of the nuclear Hamiltonian. [Copyright &y& Elsevier]