  We performed general relativistic, long-term, axisymmetric neutrino radiation
hydrodynamics simulations for the remnant formed after the binary neutron star
merger, which consist of a massive neutron star and a torus surrounding it. As
an initial condition, we employ the result derived in a three-dimensional,
numerical relativity simulation for the binary neutron star merger. We
investigate the properties of neutrino-driven ejecta. Due to the
pair-annihilation heating, the dynamics of the neutrino-driven ejecta is
significantly modified. The kinetic energy of the ejecta is about two times
larger than that in the absence of the pair-annihilation heating. This suggests
that the pair-annihilation heating plays an important role in the evolution of
the merger remnants. The relativistic outflow, which is required for driving
gamma-ray bursts, is not observed because the specific heating rate around the
rotational axis is not sufficiently high due to the baryon loading caused by
the neutrino-driven ejecta from the massive neutron star. We discuss the
condition for launching the relativistic outflow and the nucleosynthesis in the
ejecta.
