We measure the $B^0$ lifetime and flavor-oscillation frequency using $B^0\to D^{ (*)-}\pi^+$ decays collected by the Belle II experiment in asymmetric-energy $e^+e^-$ collisions produced by the SuperKEKB collider operating at the $\Upsilon(4S)$ resonance. We fit the decay-time distribution of signal decays, where the initial flavor is determined by identifying the flavor of the other $B$ meson in the event. The results, based on $33000$ signal decays reconstructed in a data sample corresponding to ${ 190}\text{ fb}^{ -1}$, are $\tau_{ B^0} = { 1.499}\pm{ 0.013}\pm{ 0.008}\;\text{ ps}$, $\Delta m_d = { 0.516}\pm{ 0.008}\pm{ 0.005}\;\text{ ps}^{ -1}$, where the first uncertainties are statistical and the second are systematic. These results are consistent with the world-average values.
Categories: hep-ex