  We theoretically study the tunneling time by investigating a wave packet of
Bose-condensed atoms passing through a square barrier. We find that the
tunneling time exhibits different scaling laws in different energy regimes. For
negative incident energy of the wave packet, counterintuitively, the tunneling
time decreases very rapidly with decreasing incident velocity. In contrast, for
positive incident energy smaller than the barrier height, the tunneling time
increases slowly and then reaches a maximum, which is in agreement with the
Larmor clock experiments. The effect of the barrier width related to the
uncertainty principle on the maximum tunneling time is also addressed. Our work
provides a general scenario of tunneling time that can be used to understand
and explain the controversy over tunneling time.
