Spectra and scattering of light lattice nuclei from effective field theory

An effective field theory is used to describe light nuclei, calculated from quantum chromodynamics on a lattice at unphysically large pion masses. The theory is calibrated at leading order to two available data sets on two- and three-body nuclei for two pion masses. At those pion masses we predict the quartet and doublet neutron-deuteron scattering lengths, and the α-particle binding energy. For mπ=510 MeV we obtain, respectively, 4anD=2.3±1.3 fm, 2anD=2.2±2.1 fm, and Bα=35±22 MeV, while for mπ=805 MeV 4anD=1.6±1.3 fm, 2anD=0.62±1.0 fm, and Bα=94±45 MeV are found. Phillips- and Tjon-like correlations to the triton binding energy are established. We find the theoretical uncertainty in the respective correlation bands to be independent of the pion mass. As a benchmark, we present results for the physical pion mass, using experimental two-body scattering lengths and the triton binding energy as input. Hints of subtle changes in the structure of the triton and α particle are discussed.