E1 strength distribution of ¹¹Li in Halo Effective Field Theory

One of the signatures of a halo nucleus is a low-energy enhancement of the E1 strength distribution, dB(E1)/dE. This observable can be measured in Coulomb dissociation experiments. The E1 strength distribution is sensitive to long-distance properites of the halo state, but it is also affected by final-state interactions (FSI). 

We calculate dB(E1)/dE for the two-neutron halo nucleus ¹¹Li in Halo Effective Field Theory (EFT) using the ⁹Li core and the two halo neutrons as degrees of freedom. By evaluating the multiple-scattering series order-by-order we show that the neutron-neutron final-state interaction is the dominant FSI at low energies. The comparison of leading-order Halo EFT results with experimental data from RIKEN [T. Nakamura et al., Phys. Rev. Lett. 96, 252502 (2006)] shows reasonable agreement.