  Galaxy mergers are believed to play a key role in transforming star-forming
disk galaxies into quenched ellipticals. Most of our theoretical knowledge
about such morphological transformations does, however, rely on idealised
simulations where processes such as cooling of hot halo gas into the disk and
gas accretion in the post-merger phase are not treated in a self-consistent
cosmological fashion. In this paper we study the morphological evolution of the
stellar components of four major mergers occurring at z=0.5 in cosmological
hydrodynamical zoom-simulations. In all simulations the merger reduces the disk
mass-fraction, but all galaxies simulated at our highest resolution regrow a
significant disk by z=0 (with a disk fraction larger than 24%). For runs with
our default physics model, which includes galactic winds from star formation
and black hole feedback, none of the merger remnants are quenched, but in a set
of simulations with stronger black hole feedback we find that major mergers can
indeed quench galaxies. We conclude that major merger remnants commonly evolve
into star-forming disk galaxies, unless sufficiently strong AGN feedback
assists in the quenching of the remnant.
