First observation of CP violation and measurement of polarization in B⁺→ρ(770)⁰ K^*(892)⁺ decays

2025/08/19 by R. Aaij, LHCb collaboration, A. S. W. Abdelmotteleb +2368 · 2 voices
#hep-ex

paper · pdf · doi:10.48550/arxiv.2508.13563

Abstract

An amplitude analysis of the B⁺→(π⁺π^-)(K⁰_Sπ⁺) decay is performed in the mass regions 0.30 < m_π⁺π^- < 1.10 GeV/c² and 0.75 < m_K⁰_Sπ⁺ < 1.20 GeV/c², using pp collision data recorded with the LHCb detector corresponding to an integrated luminosity of 9 fb^-1. The polarization fractions and CP asymmetries for B⁺→ρ(770)⁰K^*(892)⁺ decays are measured. Violation of the CP symmetry in the decay B⁺→ρ(770)⁰K^*(892)⁺ is observed for the first time, with a significance exceeding nine standard deviations. The CP asymmetry is measured to be \cal A_CP = 0.507 ± 0.062 (stat) ± 0.024 (syst) and the CP-averaged longitudinal polarization fraction of f_L = 0.720 ± 0.028 (stat) ± 0.009 (syst). The measurements help to shed light on the polarization puzzle of B mesons decaying to two vector mesons.

Citations

• Improved global determination of two-meson distribution amplitudes from multi-body B decays
• Geant4 developments and applications
• Final State Interactions in Hadronic B Decays
• The Large-Sample Distribution of the Likelihood Ratio for Testing Composite Hypotheses
• Partial wave analysis in K‐matrix formalism

Discussions

• First observation of CP violation and measurement of polarization in B⁺→ρ(770)⁰K*(892)⁺ decays arxiv.org/abs/2508.13563 - The CP asymmetry is measured to be 0.507±0.062)±0.017 and the CP-averaged long [bsky, 6 points, 0 comments]
• #LHCbpaper: First observation of CP violation and measurement of polarisation in B⁺ → ρ⁰(770) K*(892)⁺ decays (arXiv:2508.13563) https://arxiv.org/abs/2508.13563 [bsky, 2 points, 0 comments]

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