https://hdl.handle.net/20.500.12294/3340 Tue, 10 Nov 2026 23:31:10 GMT 2026-11-10T23:31:10Z https://hdl.handle.net/20.500.12294/3974 Measurement of the B0 lifetime and flavor-oscillation frequency using hadronic decays reconstructed in 2019-2021 Belle II data Kolcu, O. B.; BESIII Collaboration We measure the B0 lifetime and flavor-oscillation frequency using B0→D(∗)-π+ decays collected by the Belle II experiment in asymmetric-energy e+e- collisions produced by the SuperKEKB collider operating at the ϒ(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 fb-1, are τB0=(1.499±0.013±0.008) ps, Δmd=(0.516±0.008±0.005) ps-1, where the first uncertainties are statistical and the second are systematic. These results are consistent with the world-average values. © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3. Sun, 01 Jan 2023 00:00:00 GMT https://hdl.handle.net/20.500.12294/3974 2023-01-01T00:00:00Z https://hdl.handle.net/20.500.12294/3973 Observation of ψ(3770) → ηJ/ψ Kolcu, O. B.; BESIII Collaboration Using a data sample collected with the BESIII detector operating at the BEPCII storage ring, the Born cross section of the process e+e- -> eta J=psi at a center-of-mass energy pffisffi = 3.773 GeV is measured to be (8.88 +/- 0.87 +/- 0.42) pb. We fit the cross section line shape before correcting for the initial state radiation ffiffifromps = 3.773 to 4.600 GeV to obtain the branching fraction B(psi(3770) -> eta J=psi). We obtain B(psi(3770) -> eta J=psi) = (11.3 +/- 5.9 +/- 1.1) x 10-4 when the psi(3770) decay amplitude is added coher-ently to the other contributions, and (8.7 +/- 1.0 +/- 0.8) x 10-4 when it is added incoherently. Here the quoted uncertainties are statistical and systematic, respectively. In both cases, the statistical significance of psi(3770) resonance is above 7 sigma. This is the first time the decay psi(3770) -> eta J=psi is observed with a statistical significance greater than 5 sigma. Sun, 01 Jan 2023 00:00:00 GMT https://hdl.handle.net/20.500.12294/3973 2023-01-01T00:00:00Z