Electric Properties of One-Neutron Halo Nuclei in Halo EFT

Abstract

We exploit the separation of scales in weakly-bound nuclei to compute E2 transitions and electric form factors in a Halo EFT framework. The relevant degrees of freedom are the core and the halo neutron. The EFT expansion is carried out in powers of R core /R halo , where R core and R halo denote the length scales of the core and halo, respectively. We include the strong s-wave and d-wave interactions by introducing dimer fields. The dimer propagators are regulated by employing the power divergence subtraction scheme and matched to the effective range expansion in the respective channel. Electromagnetic interactions are included via minimal substitution in the Lagrangian. We demonstrate that, depending on the observable and respective partial wave, additional local gauge-invariant operators contribute in LO, NLO and higher orders. * This work has been supported by Deutsche Forschungsgemeinschaft (SFB 1245).

Effective field theory description of halo nuclei

“…In Ref. [58], an alternative power counting for d-wave bound states was proposed and applied to the description of the J P = 5/2 + excited state of 15 C and its E2 transitions to the J P = 1/2 + ground state. This power counting requires two fine tunings.…”

“…In [58], an alternative power counting for d-wave bound states was proposed and applied to the description of the J 5 2 P = + excited state of 15 C and its E2 transitions to the couples to an n a pair with l=2 in the final state. However, they used dimensional regularization with minimal subtraction which sets all power-law divergences automatically to zero and thus may have missed some contributions.…”

“…Moreover, universality for resonant p-wave interactions is weaker as two parameters, the p-wave scattering volume and effective range, are required already at leading order in the two-body system. In higher partial waves this pattern gets progressively worse [18,57,58]. Nevertheless, universality still provides powerful constraints for the structure and dynamics of halo nuclei [59,52].…”