Search

We discuss the current status of chiral effective field theory in the three-nucleon sector and present selected results for nucleon–deuteron scattering observables based on semilocal momentum-space-regularized chiral two-nucleon potentials together with consistently regularized three-nucleon forces up to third chiral order. Using a Bayesian model for estimating truncation errors, the obtained results are found to provide a good description of the experimental data. We confirm our earlier findings that a high-precision description of nucleon–deuteron scattering data below pion production threshold will require the theory to be pushed to fifth chiral order. This conclusion is substantiated by an exploratory study of selected short-range contributions to the three-nucleon force at that order, which, as expected, are found to have significant effects on polarization observables at intermediate and high energies. We also outline the challenges that will need to be addressed in order to push the chiral expansion of three-nucleon scattering observables to higher orders. [ABSTRACT FROM AUTHOR]

We discuss the uncertainties in constraining low-energy constants of chiral effective field theory from H $ \beta$ decay. The half-life is very precisely known, so that the Gamow-Teller matrix element has been used to fit the coupling $ c_D$ of the axial-vector current to a short-range two-nucleon pair. Because the same coupling also describes the leading one-pion-exchange three-nucleon force, this in principle provides a very constraining fit, uncorrelated with the H binding energy fit used to constrain another low-energy coupling in three-nucleon forces. However, so far such H half-life fits have only been performed at a fixed cutoff value. We show that the cutoff dependence due to the regulators in the axial-vector two-body current can significantly affect the Gamow-Teller matrix elements and consequently also the extracted values for the $ c_D$ coupling constant. The degree of the cutoff dependence is correlated with the softness of the employed NN interaction. As a result, present three-nucleon forces based on a fit to H $ \beta$ decay underestimate the uncertainty in $ c_D$ . We explore a range of $ c_D$ values that is compatible within cutoff variation with the experimental H half-life and estimate the resulting uncertainties for many-body systems by performing calculations of symmetric nuclear matter. [ABSTRACT FROM AUTHOR]

This erratum fixes an error in the use of the low-energy constant in the two-body currents. The corrected version of one of the equations and of some of the figures is reported. [ABSTRACT FROM AUTHOR]