# Measurement of the $B^0$ lifetime and flavor-oscillation frequency using hadronic decays reconstructed in 2019-2021 Belle II data

## TL;DR

This paper reports precise measurements of the $B^0$ meson lifetime and flavor-oscillation frequency using hadronic decay data from the Belle II experiment, confirming consistency with world averages.

## Contribution

First measurement of $B^0$ lifetime and oscillation frequency using Belle II data with improved precision and methodology.

## Key findings

- $B^0$ lifetime measured as 1.499 ps
- Oscillation frequency $ riangle m_d$ measured as 0.516 ps$^{-1}$
- Results agree with world averages

## Abstract

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.