Electromagnetic structure ofA=2and 3 nuclei in chiral effective field theory

Abstract

The objectives of the present work are twofold. The first is to address and resolve some of the differences present in independent, chiral-effective-field-theory (χEFT) derivations up to one loop, recently appeared in the literature, of the nuclear charge and current operators. The second objective is to provide a complete set of χEFT predictions for the structure functions and tensor polarization of the deuteron, for the charge and magnetic form factors of 3 He and 3 H, and for the charge and magnetic radii of these few-nucleon systems. The calculations use wave functions derived from high-order chiral two-and three-nucleon potentials and Monte Carlo methods to evaluate the relevant matrix elements. Predictions based on conventional potentials in combination with χEFT charge and current operators are also presented. There is excellent agreement between theory and experiment for all these observables for momentum transfers up to q 2.0-2.5 fm −1 ; for a subset of them, this agreement extends to momentum transfers as high as q ≃ 5-6 fm −1 . A complete analysis of the results is provided.

Minimally nonlocal nucleon-nucleon potentials with chiral two-pion exchange includingΔresonances

“…It is should be noted that this observable has negligible contributions due to two-body electromagnetic operators [65]. The magnetic moment, µ d , and quadrupole moment, Q d , experimental values are underestimated by all three models, but these observables are known to have significant corrections from (isoscalar) two-body terms in nuclear electromagnetic charge and current [65]. Their inclusion would bring the calculated values considerably closer to, if not in agreement with, experiment.…”

“…The deuteron (matter) radius, r d , is exactly reproduced with model b, but is under-predicted (over-predicted) by about 1.4% (0.7%) with model a (model c). It is should be noted that this observable has negligible contributions due to two-body electromagnetic operators [65]. The magnetic moment, µ d , and quadrupole moment, Q d , experimental values are underestimated by all three models, but these observables are known to have significant corrections from (isoscalar) two-body terms in nuclear electromagnetic charge and current [65].…”

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

“…The inclusion of 3N interactions in the initial Hamiltonian is crucial for achieving this good reproduction of the experimental level data: It stabilizes the spacing between the neutron 0d 3/2 orbital and the other levels in the sd-shell as neutrons are added, which governs the energies of low-lying excitations and the location of the neutron drip line [55,128,160,163]. We note that the excited states in 23,24 O are overestimated to some degree, but this is expected because our Shell model calculations do not explicitly treat the continuum coupling at present, and the N N +3N (400) Hamiltonian produces a too-pronounced shell closure at N = 16 (see section 6.1).…”

“…Instead, we start from nuclear interactions that describe low-energy QCD observables in the N N and 3N systems, like scattering data or binding energies. Nowadays, such interactions are derived in Chiral Effective Field Theory (EFT), which provides a constructive framework and organizational hierarchy for N N , 3N , and higher many-nucleon forces, as well as consistent electroweak operators (see, e.g., [14][15][16][17][18][19][20][21][22][23][24][25]). Since Chiral EFT is a lowmomentum expansion, high-momentum (short-range) physics is not explicitly resolved by the theory, but parametrized by the so-called low-energy constants (LECs).…”

Toward order-by-order calculations of the nuclear and neutron matter equations of state in chiral effective field theory

“…We fix the low-energy constants c D and c E that appear in the N 2 LO 3NF within the three-nucleon sector. Specifically, we constrain them to reproduce binding energies of A = 3 nuclei together with the Gamow-Teller matrix element in tritium β-decay, following a well established procedure [21,[28][29][30][31][32][33]. The values of c D and c E are given in Table II for the different chiral orders and cutoff scales.…”