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Observation of CP Violation in B^{0}→J/ψρ(770)^{0} Decays
R Aaij1, A S W Abdelmotteleb2, C Abellan Beteta3
1Nikhef National Institute for Subatomic Physics, Amsterdam, Netherlands.
Physical Review Letters
|July 31, 2026
Summary
This study reports the first observation of time-dependent CP violation in B0→J/ψρ(770)0 decays. The measurements provide the most stringent constraint on the penguin contribution to CP violation in B0s→J/ψϕ(1020) decays.
Area of Science:
- High Energy Physics
- Particle Physics
- Quantum Chromodynamics
Background:
- CP symmetry violation is a key phenomenon in particle physics.
- Understanding CP violation in B meson decays is crucial for testing the Standard Model.
- Previous measurements have hinted at CP violation, but direct observation in specific channels is needed.
Purpose of the Study:
- To measure the time-dependent CP asymmetry in B0→J/ψρ(770)0 decays.
- To provide the first observation of time-dependent CP violation in this decay channel.
- To constrain the penguin contribution to CP violation in B0s→J/ψϕ(1020) decays.
Main Methods:
- Analysis of proton-proton collision data collected by the LHCb detector at 13 TeV.
- Measurement of CP-violating parameters using a large dataset (6 fb⁻¹).
- Application of SU(3) flavor symmetry to combine results with previous measurements.
Main Results:
- First observation of time-dependent CP violation in B0→J/ψρ(770)0 decays.
- Determination of CP-violation parameters: 2βeffcc¯d = 0.710 ± 0.084 ± 0.051 rad and |λ| = 1.019 ± 0.034 ± 0.024.
- Most stringent constraint on the penguin contribution Δϕs to the CP-violating phase ϕs in B0s→J/ψϕ(1020) decays: Δϕs = 5.0 ± 4.6 mrad.
Conclusions:
- Time-dependent CP violation is confirmed in B0→J/ψρ(770)0 decays.
- The results offer valuable insights into CP violation mechanisms in the heavy quark sector.
- This study significantly advances our understanding of fundamental CP symmetry in particle physics.
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