Sensitivities and correlations of nuclear structure observables emerging from chiral interactions

Abstract

Starting from a set of different two-and three-nucleon interactions from chiral effective field theory, we use the importance-truncated no-core shell model for ab initio calculations of excitation energies as well as electric quadrupole (E2) and magnetic dipole (M1) moments and transition strengths for selected p-shell nuclei. We explore the sensitivity of the excitation energies to the chiral interactions as a first step towards and systematic uncertainty propagation from chiral inputs to nuclear structure observables. The uncertainty band spanned by the different chiral interactions is typically in agreement with experimental excitation energies, but we also identify observables with notable discrepancies beyond the theoretical uncertainty that reveal insufficiencies in the chiral interactions. For electromagnetic observables we identify correlations among pairs of E2 or M1 observables based on the ab initio calculations for the different interactions. We find extremely robust correlations for E2 observables and illustrate how these correlations can be used to predict one observable based on an experimental datum for the second observable. In this way we circumvent convergence issues and arrive at far more accurate results than any direct ab initio calculation. A prime example for this approach is the quadrupole moment of the first 2 + state in 12 C, which is predicted with an drastically improved accuracy.

Computing the dipole polarizability of Ca48 with increased precision

“…Often, the largest uncertainty results from truncations of the employed chiral effective field theory at some given order in the power counting, whereas statistical uncertainties due to the optimization of the interaction are significantly smaller [50,66,67]. While a robust quantification of systematic uncertainties related to the employed chiral interactions is still lacking, a rough estimate can be made by employing a large set of different chiral interactions [36,48,60,68,69]. Uncertainties from finite harmonic-oscillator basis can be estimated by varying the number of oscillator shells (N max ) and the oscillator frequency ( ̵ hΩ).…”

In-medium similarity renormalization group for closed and open-shell nuclei

“…. forces [56,91], so we have to reconsider the uncertainties due to these omitted terms for other interactions and observables (see, e.g., [150]). …”

CanAb InitioTheory Explain the Phenomenon of Parity Inversion inBe11?

“…Peculiar also is the electricdipole transition strength between the two bound states, which has attracted much attention since its first measurement in 1971 [5] and was remeasured in 1983 [6] and 2014 [7]. It is the strongest known transition between low-lying states, attributed to the halo character of 11 Be.An accurate description of this complex spectrum is anticipated to be sensitive to the details of the nuclear force [8], such that a precise knowledge of the nucleon-nucleon (NN) interaction, desirably obtained from first principles, is crucial. Moreover, the inclusion of three-nucleon (3N) effects has been found to be indispensable for an accurate description of nuclear systems [9,10].…”

“…An accurate description of this complex spectrum is anticipated to be sensitive to the details of the nuclear force [8], such that a precise knowledge of the nucleon-nucleon (NN) interaction, desirably obtained from first principles, is crucial. Moreover, the inclusion of three-nucleon (3N) effects has been found to be indispensable for an accurate description of nuclear systems [9,10].…”