Gauss-Bonnet supergravity in six dimensions

The supersymmetrization of curvature squared terms is important in the study of the low-energy limit of compactified superstrings where a distinguished role is played by the Gauss-Bonnet combination, which is ghost-free. In this letter, we construct its off-shell ${cal N} = (1, 0)$ supersymmetrization in six dimensions for the first time. By studying this invariant together with the supersymmetric Einstein-Hilbert term we confirm and extend known results of the $alpha$-corrected string theory compactified to six dimensions. Finally, we analyze the spectrum about the ${rm AdS}_3times{rm S}^3$ solution.