Time-dependent $CP$ violation results at Belle II

TL;DR

This paper reports updated measurements of time-dependent $CP$ violation parameters at Belle II, demonstrating the detector's performance and presenting new results on $ ext{sin}2eta$ sensitive to potential new physics, based on data from 2019-2022.

Contribution

The paper provides the first measurements of $B^0$ lifetime, mixing frequency, and $CP$-violating phase at Belle II, along with three new results on $ ext{sin}2eta$ in $b o qar{q}s$ transitions, using the full dataset.

Findings

Measurements of $B^0$ lifetime and mixing frequency consistent with expectations.

First $CP$-violation measurements at Belle II with partial dataset.

Three new $ ext{sin}2eta$ results sensitive to non-SM physics.

Abstract

We report updates on time-dependent $CP$-violation observables at Belle II. The benchmark measurements of the $B^0$ lifetime $\tau_{B^0}$ and mixing frequency $\Delta m_d$ using flavor specific hadronic decays and the determination of the $CP$-violating phase $\sin2\phi_1$ in $b\to c\overline{c}s$ transitions have been performed using data collected between 2019-2021. These analyses use only half of the current available dataset and are still statistically limited, showing the excellent performance of the detector and readiness of the analysis tools. We present three new results on the effective value of $\sin2\phi_1$ in $b\to q\overline{q}s$ transitions, which are highly sensitive to generic non-Standard Model (SM) physics amplitudes, using the full dataset collected between 2019-2022.