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First Measurement of Time-Dependent CP Violation in the Flavor-Changing Neutral-Current Decay
R Aaij1, A S W Abdelmotteleb2, C Abellan Beteta3
1Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands.
Physical Review Letters
|June 26, 2026
Summary
This study analyzed B0 decays to muon pairs, measuring CP violation parameters. The results align with the Standard Model, marking the first experimental investigation of time-dependent CP violation in b→sℓℓ processes.
Area of Science:
- Particle Physics
- High Energy Physics
- Quantum Chromodynamics
Background:
- CP violation is a key phenomenon in particle physics, crucial for understanding matter-antimatter asymmetry.
- The Standard Model predicts specific CP violation parameters in B meson decays.
- Previous studies have explored CP violation, but time-dependent analyses in specific decay channels are ongoing.
Purpose of the Study:
- To perform a flavor-tagged, time-dependent analysis of B0→KS0μ+μ- decays.
- To measure CP violation parameters C and S in the b→sℓ+ℓ- decay.
- To test the predictions of the Standard Model in this decay channel.
Main Methods:
- Utilized proton-proton collision data from the LHCb experiment (2011-2018).
- Analyzed B0→KS0μ+μ- decays across the dimuon mass spectrum, excluding J/ψ and ψ(2S) resonances.
- Performed a flavor-tagged, time-dependent analysis to extract CP violation parameters.
Main Results:
- Determined CP violation parameters: C = -0.13 ± 0.32 (stat) ± 0.04 (syst) and S = +0.82 ± 0.29 (stat) ± 0.05 (syst).
- Observed results consistent with the Standard Model predictions.
- This represents the first experimental measurement of time-dependent CP violation in b→sℓ+ℓ- decays.
Conclusions:
- The measured CP violation parameters are consistent with the Standard Model.
- This study provides crucial experimental data for understanding CP violation in rare B meson decays.
- The findings contribute to the ongoing quest for physics beyond the Standard Model.
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