  Star formation efficiency controlled by the protostellar outflow in a single
cloud core is investigated by three-dimensional resistive MHD simulations.
Starting from the prestellar cloud core, the star formation process is
calculated until the end of the main accretion phase. In the calculations, the
mass of the prestellar cloud is parameterized. During the star formation, the
protostellar outflow is driven by the circumstellar disk. The outflow extends
also in the transverse direction until its width becomes comparable to the
initial cloud scale, and thus, the outflow has a wide opening angle of >40
degrees. As a result, the protostellar outflow sweeps up a large fraction of
the infalling material and ejects it into the interstellar space. The outflow
can eject at most over half of the host cloud mass, significantly decreasing
star formation efficiency. The outflow power is stronger in clouds with a
greater initial mass. Thus, the protostellar outflow effectively suppresses
star formation efficiency in a massive cloud. The outflow weakens significantly
and disappears in several free-fall timescales of the initial cloud after the
cloud begins to collapse. The natal prestellar core influences the lifetime and
size of the outflow. At the end of the main accretion phase, a massive
circumstellar disk comparable in mass to the protostar remains. Calculations
show that typically, ~30% of the initial cloud mass is converted into the
protostar and ~20% remains in the circumstellar disk, while ~40% is ejected
into the interstellar space by the protostellar outflow. Therefore, a single
cloud core typically has a star formation efficiency of 30-50%.
