We construct an effective field theory of a two-neutron halo nucleus in the limit where the two-neutron separation energy and the neutron-neutron two-body virtual energy are smaller than any other energy scale in the problem, but the scattering between the core and a single neutron is not fine-tuned, and the Efimov effect does not operate. The theory has one dimensionless coupling, which formally runs to a Landau pole in the ultraviolet. I will demonstrate some universal properties of the system, such as the ratio of the mean-square matter radius and charge radius and the shape of the E1 dipole strength function. I will also discuss the application of our EFT to 22C nucleus, where higher-order corrections to our theory are estimated as of order 20% or less if the two-neutron separation energy is less than 100 keV and the s-wave scattering length between a neutron and a 20C nucleus is less than 2.8 fm.

[Ref]
– M. Hongo, D. T. Son, arXiv:2201.09912 [nucl-th]