  A novel experiment, aiming at demonstrating the feasibility of hypernuclear
spectroscopy with heavy-ion beams, was conducted. Using the invariant mass
method, the spectroscopy of hypernuclear products of 6Li projectiles on a
carbon target at 2 AGeV was performed. Signals of the \Lambda-hyperon and
3\Lambda H and 4\Lambda H hypernuclei were observed for final states of
p+\pi^-, 3He+\pi^- and 4He+\pi^-, respectively, with significance values of
6.7, 4.7 and 4.9\sigma. By analyzing the proper decay time from secondary
vertex distribution with the unbinned maximum likelihood fitting method, their
lifetime values were deduced to be $262 ^{+56}_{-43} \pm 45$ ps for \Lambda,
$183 ^{+42}_{-32} \pm 37$ ps for 3\Lambda H, and $140 ^{+48}_{-33}\pm 35 $ ps
for 4\Lambda H.
