  Preliminary limits on the D^0 mixing parameter y = \Delta \Gamma / 2 \Gamma
are obtained using about 57.8 fb^-1 of data collected by BaBar in 2000 and
2001:y = (1.4 \pm 1.0 (stat.) +0.6 -0.7 (syst.))%. y is extracted, provided
that CP is conserved, by measuring separately the D^0 lifetime for the
Cabibbo-suppressed decay modes K- K+, \pi- \pi+ and the Cabibbo-favoured mode
K- \pi+. Backgrounds are suppressed by D*-tag and particle identification
requirements.
