  We examine nucleosynthesis in the ejecta of black hole-neutron star mergers
based on the results of self-consistent, long-term
neutrino-radiation-magnetohydrodynamics simulations for the first time. We find
that the combination of dynamical and post-merger ejecta reproduces a
solar-like r-process pattern. Moreover, the enhancement level of actinides is
highly sensitive to the distribution of both electron fraction and the velocity
of the dynamical ejecta. Our result implies that the mean electron fraction of
dynamical ejecta should be ~ 0.05-0.08 in order to reconcile the
nucleosynthetic abundances with those in r-process-enhanced, actinide-boosted
stars. This result provides an important constraint for nuclear equations of
state.
